Color wheel assembly and color sequential display device using the same, color wheel unit and color sequential display device using the same, and color sequential display device

ABSTRACT

A field sequential color display device includes a color wheel assembly. The color wheel assembly has a color wheel which is divided into a plurality of color regions and a motor for rotating the color wheel. The motor contains a sensor for detecting rotation of the motor and the sensor outputs at least one pulse per one revolution of the motor. The color wheel assembly also has a spatial light modulator for displaying image data that is driving in synchronization with the pulse output by the sensor.

FIELD OF THE INVENTION

The present invention relates to a display device using a spatial lightmodulator (SLM) or light valve which works at a considerably high speedand, more particularly, to a color wheel assembly and a field sequentialcolor display device using the same, a color wheel unit and a fieldsequential color display device using the same, and a field sequentialcolor display device, to display colors in a time-multiplexing and colorsequential manner.

BACKGROUND OF THE INVENTION

In recent years, attention has been increasingly focused on large screendisplays such as home theaters and presentations, and projectors arerecently being commercialized which use a small reflective light valveof a liquid crystal on silicon (hereinafter, referred to as LCOS) inwhich a switching element, a reflection electrode or the like is formedon a silicon substrate or a digital micromirror device (hereinafter,referred to as DMD), and enlargedly project a display image with aprojection lens to obtain a large screen display image.

The LCOS is one of the SLMs, and it has reflection pixels in a form ofmatrix, and can switch displays at a high speed using a video signal. Inorder to display moving pictures at a video rate, it is necessary thatvideo of 60 frames can be displayed within one field. For that purpose,the liquid crystal response speed of at least 1/60=16.7 msec or lower isrequired. Further, in order to display at least three colors (RGB)during that time, a response speed of 5.6 msec is required. As examplesof such a high-speed response liquid crystal, there are a ferroelectricliquid crystal, an antiferroelectric liquid crystals, an OCB (opticallyCompensated Bend) liquid crystal and the like in the OCR liquid crystal,a Bend orientation cell is used to self-compensate changes in thevisibility angle direction using birefringence of the liquid crystal,and when this liquid crystal is combined with a negative opticalcompensation film, a wider visibility angle is realized, as well as ahigh-speed response is enabled.

The DMD is one of the SLMs, and is mainly used as a projection-typedisplay. The DMD has hundreds of thousands or one million or moreextremely minute mirrors on one chip, each of the mirrors correspondingto one pixel. ON/OFF of the DMD is controlled by inclining these mirrorsto change the reflection angles of beams which are incident on themirrors. For that purpose, the respective mirrors are mounted to one ormore hinges which are mounted on a supporting post, and are separatedfrom a control circuit situated below by an air gap. This controlcircuit applies static electricity, which selectively inclines therespective mirrors. When this is applied to a display, image data areloaded on a memory cell of the DMD, and the mirrors are inclined on thebasis of these data to reflect light toward the ON direction or awayfrom the ON direction.

As methods adopted in the projectors, when classified according to thenumber of SLMs required in the projector, a single-panel type and athree-panel type are mainly used. As an example of the three-panel-typeprojectors, there is one which modulates light beams of respectivecolors, which has been subjected to the color separation, by thecorresponding SLMs, respectively, and then performs the colorcomposition while projecting the light on a screen. In this method,three SLMs are used in parallel, the respective being used for red (R),green (G), and blue (B). On the other hand, in the single-panel-typeprojector, only one SLM is used, and R, G and B light beams aremodulated successively in a time-multiplexing manner, or spatially inunits of area or pixel, while using a single-panel SLM. Accordingly, inthe single-panel-type projector which requires only one SLM, requests tohardware relating to the SLM are only one-third of those in thethree-panel-type projector which requires three SLMs. This is notrestricted to the projectors, but applies to all color display devicesusing the SLMs.

Hereinafter, the color display device using the single-panel projectoris described.

As an example of the color display device using the single-panelprojector, there is a time-multiplexing color sequential type colordisplay device utilizing a time-multiplexing color mixture. In thistime-multiplexing color sequential method, the pixels have red, greenand blue values, respectively, and during each frame period, the pixelsin the frame are addressed successively according to red, blue, and thengreen data. On the other hand, filters of the same colors as thesecolors are positioned in the form of a disk, a color wheel having atleast three different color regions is synchronized with these data, anddata corresponding to the respective colors are displayed by the SLM. Atthis time, the band of light incident on the SLM is controlled by thecolor wheel. As described above, the time-multiplexing field sequentialcolor display device enables color display in a time-multiplexing mannerand, when the time-multiplexing rate is higher than the standard displayspeed of 60 images/sec, the images are perceived by the eyes to haveoriginal colors.

The above-mentioned prior art field sequential color display deviceusing the color filter is described with reference to FIG. 36. FIG. 36is a diagram schematically illustrating an example of the prior artfield sequential color display device using the color wheel. As shown inFIG. 36, the field sequential color display device comprises a lamp1001, an ellipsoidal mirror 1002, an UV-IR cut-off filter 1003, a colorwheel 1004, a condensing lens 1005, a field lens 1006, a reflective LCOS1007, and a projection lens 1008.

The lamp 1001 is a discharging-type high output lamp such as a xenonlamp, a metal halide lamp, and an extra-high pressure mercury lamp.

The reflective LCOS 1007 is one of the SLM.

The color wheel 1004 is preferably situated in a position where beamsare condensed the most. This is because the SLM should be turned off toprevent color mixture, while the color wheel is being rotated and a beamspot is passing through the boundary of the different color filters, andthe shorter the OFF time is, the higher the temporal opening ratio is,whereby brighter displays are enabled. Therefore, it is preferable thatthe condensation spot on the color filter should be smaller tominiaturize the color wheel, otherwise a color wheel having a largerouter diameter is required, resulting in a considerably large size ofthe entire system.

The operation of the so-constructed prior art field sequential colordisplay device is described. The lamp 1001 is positioned approximatelyin a focus position of the ellipsoidal mirror 1002 as a concave mirror,so that the emitted white light beams are condensed by the ellipsoidalmirror 1002 on the color filter of the color wheel 1004. The UV-IRcut-off filter 1003 filters out ultraviolet and infrared rays of thelight emitted from the lamp 1001. The color wheel 1004 comprises red,blue, and green color filters which are positioned in the form of a diskand, in synchronization with the filtering of beams by the respectivecolor filters, the LCOS 1007 displays image frames of the beam color.Normally, the color wheel 1004 is rotated one revolution per image framein 1/60 sec, or at 3600 rpm. The condensing lens 1005 efficientlycondenses light which is transmitted through the color wheel 1004, andirradiates the LCOS 1007. The field lens 1006 is used for condensinglight which is transmitted through the LCOS 1007 on the projection lens1008.

In this prior art field sequential color display device, there are atleast three color sub-frames during one frame frequency, the sub-framesbeing red, green and blue, respectively. The LCOS 1007 switches displayimages at a considerably high speed for the respective colors, andmodulated beams of respective colors are enlargedly projected on ascreen (not shown) by using the projection lens 1008. Since videos ofthe respective colors (R, G and B) are successively projected anddisplayed on the screen in 1/60 sec, these videos are perceived by theeyes as after-images, whereby full-color videos are recognized. In theabove-mentioned prior art time-multiplexing color sequential type colordisplay device, the color wheel is rotated by a motor or the like at ahigh speed. Therefore, it is quite important how the rotation speed andphase of the color wheel are controlled, to accurately and preciselyacquire timing information for switching the colors of red, green andblue, and further control the SLM to perform modulation insynchronization with the color.

Accordingly, in the prior art field sequential color display device, areflective photo-sensor has been commonly used for detecting theposition of the color wheel. FIG. 37 is a schematic diagram illustratinga color wheel, and a cross-sectional view illustrating a color wheelassembly which is constituted by a color wheel and a motor. A hub 372 ofthe color wheel 1004 is painted black in its entirety, and an aluminumtape 373 is pasted as an index mark at a position of the joint part of agreen filter 1004G and a red filter 1004R. The reflective photo-sensor374 is mounted on a case 375 which houses the color wheel 1004, and whenthe color wheel 1004 is rotated, the reflective photo-sensor 374 detectsthe aluminum tape as a reflecting surface and generates a pulse signalof one pulse per one revolution. Thereby, the control circuit of the SLMperforms the switching from a green video drive signal to a red videodrive signal, as well as controls the rotation speed and phase of themotor so that the color wheel 1004 is rotated at one frame frequency. Anexample of the method for receiving a pulse feedback from the colorwheel and controlling the rotation speed and phase of the motor isdescribed in detail in U.S. Pat. No. 5,868,482.

In the above-mentioned prior art field sequential color display deviceusing the color wheel, when a desired display quality is to be obtainedwithout color separation, the number of revolutions of the color wheel1004 should be about 10000 rpm or larger. However, in this high-speedrotation, the centrifugal force applied to the color wheel 1004 becomesquite large, whereby the aluminum tape 373 pasted on the color wheel1004 as the index mark is soon peeled off and flew into pieces.

In addition, since the color wheel 1004 is positioned in close proximityto the lamp 1001 as well as the beams which have condensed in a smallspot on the color wheel 1004 are subjected to the color separation, thecolor wheel 1004 is easily affected by the heat and its temperatureimmediately rises at 70° C. or more. Accordingly, the adhesive of thealuminum tape 373 bonded on the color wheel 1004 as the index mark has apoor adhesion as compared to room temperatures. Therefore, the tape 373becomes more easily peeled off. Further, when the color wheel is housedin the case, the temperature of the color wheel case itself is increaseddue to heat radiated from the lamp or absorption of unnecessary light,whereby it becomes difficult to cool the color wheel and the motor inthe case.

Further, in the manufacture of the color wheel, steps of painting thehub 372 in black, and positioning and bonding the aluminum tape 373 asthe index mark on the hub are required. Further, the color wheel ishoused in the case to be protected from the dust, and therefore, a stepof installing the photo-sensor 374 for detecting the index mark formedon the color wheel 1004, at a predetermined position of the color wheelcase 375 is required. These steps both should be carried out accurately,which leads to increases in costs.

Further, a motor 371 is mounted at an opening below the flange of thecolor wheel 1004, and the color wheel 1004 is rotated by the motor inthe case 375. At this time, the photo-sensor 374 for detecting the indexmark is mounted on the case 375 so as to protrude toward the color wheel1004. As shown in FIG. 37, the color wheel 1004 opposes to a bottomsurface 375 a and a case lid 375 b of the color wheel case body 375. Thecolor wheel 1004 is in proximity the bottom surface of the color wheelcase body 375.

When the color wheel 1004 is rotated, the circumferential speeds aredifferent between in the vicinity of the rotation axis and the outercircumference part. Therefore, an air current from the center of thecolor wheel 1004 toward the outer radius occurs in a gap between thecolor wheel 1004 and the case body 375 (shown by arrows in FIG. 37). Atthis time, the photo-sensor 374 interferes with the air current, leadingto noises.

Further, to allow the photo-sensor 374 to read the index mark, the hubarea through which light does not directly pass is required, and thispresents a problem in minimizing the diameter of the color wheel orminiaturizing.

The color wheel rotates color filters which are made of glass at a highspeed, so it is easily electrostatically charged due to friction withair when the color wheel is charged, it attracts dust in the air,thereby reducing the transmittance of the filter. Even when the colorwheel is housed in the case, since the rotation of the color wheelcreates wind pressure, and air frequently flows into or out of the gapof the case, the filters similarly become dirty with time. Especiallywhen the color wheel is housed in the case, it is necessary to providean opening for incoming or outgoing light, and the incoming/outgoing airinto/from the opening causes the dust to be caught in the case.

When the color wheel which is constituted by thin glass filters rotatesat a high speed and cuts through the air, a whistling sounds occur, andit becomes the source of large noise, together with the electromagneticsounds of the motor. Especially when the color wheel is housed in thecase, the air current is generated by the wind pressure resulting fromthe rotation of the color wheel from an opening which is provided forincoming or outgoing light, and the incoming/outgoing air into/from theopening causes noise.

In the field sequential color display device as shown in FIG. 36, acondensation spot 1009 of light emitted from the lamp 1001 is formed onthe color wheel 1004. The size of the condensation spot 1009 depends onthe size of an emitting part 1001 a of the lamp 1001, and the larger theemitting part 1001 a is, the larger the condensation spot 1009 is.

FIG. 38 is a diagram for explaining the relationship between the colorwheel 1004 and the condensation spot 1009. Hereinafter, the problems ofthe prior art field sequential color display device are described withreference to FIG. 38.

The color wheel 1004 comprises, for example, red, green and bluefan-shaped color filters 1004R, 1004G and 1004E which are combined inthe form of a disk, and a full-color display is enabled by rotating thecolor wheel in synchronization with the display of the LOOS 1007.However, when the condensation spot 1009 extends across two adjacentcolor filters, light beams which have been transmitted through the twocolor filters are incident on the LCOS simultaneously, resulting in amixture of colors, whereby an image having a different color from theone which is to be normally displayed is displayed on the screen.

Practically, while boundaries 1004RG, 1004GB and 1004BR of therespective color filters 1004R, 1004G and 1004E are passing through thecondensation spot 1009, the LCOS 1007 is controlled to display in black,i.e., in the OFF state, whereby the above-mentioned problem of colormixture is solved. (Hereinafter, the period during which the LCOS 1007is controlled to display black is referred to as a black displayperiod.)

However, it is known that the light source used in the field sequentialcolor display device, such as the lamp 1001, has the emitting part 1001a whose size (hereinafter, referred to as an arc length) varies duringthe use. Usually, the arc length tends to be longer with the lightingtime of the lamp 1001. Therefore, while the lamp 1001 is being used, thesize of the condensation spot 1009 on the color wheel 1004 is graduallyincreased and, in some cases, the period during which the condensationspot 1009 extends across two adjacent color filters becomes longer thanthe black display period of the LCOS 1007. In these cases, the initiallyset black display period cannot prevent the formation of a color-mixedoptical image on the LCOS 1007, whereby an image having a differentcolor from the one which is to be normally displayed is displayed on thescreen.

Assuming that the size of the condensation spot 1009 which is formed onthe color wheel 1004 is gradually increased with changes in the arclength of the lamp 1001, the black display period of the LCOS 1007 canbe set to be longer. However, the longer the black display period is,the more the ratio of light which irradiates the LCOS 1007 andcontributes to the original image display is reduced. Therefore, in aninitial stage of use when the arc length of the lamp 1001 is relativelyshort, an unnecessary black display period is set, whereby the lightutilization efficiency is reduced and the luminance of the imageprojected on the screen is reduced.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide a color wheelassembly comprising a color wheel and a motor for rotating the colorwheel, in which the position of the color wheel can be accuratelydetected even at high-speed rotation or at elevated temperatures, and afield sequential color display device using this color wheel assembly.

It is another object of the present invention to provide a color wheelunit comprising a color wheel, a motor, and a color wheel case, whichcan prevent noise caused by housing of the color wheel in the colorwheel case, as well as effectively cool the color wheel case, and afield sequential color display device using this color wheel unit.

It is another object of the present invention to provide a fieldsequential color display device which can prevent color mixture withoutsetting the black display period of the LCOS unnecessarily long evenwhen the size of the emitting part of the light source is increased inuse, and enables bright and high-quality image displays.

Other objects and advantages of the present invention will becomeapparent from the detailed description and specific embodimentsdescribed are provided only for illustration since various additions andmodifications within the spirit and scope of the invention will beapparent to those of skill in the art from the detailed description.

A color wheel assembly according to a 1st aspect of the presentinvention comprises a color wheel which is divided into plural colorregions, and a motor for rotating the color wheel, in which the motorcontains a sensor for detecting rotation of the motor, and the sensoroutputs at least one pulse per one motor revolution.

According to a 2nd aspect of the present invention, in the color wheelassembly of the 1st aspect, the sensor is a magnetic sensor, and themagnetic sensor outputs at least one pulse per one motor revolution.

According to a 3rd aspect of the present invention, in the color wheelassembly of the 1st aspect, the sensor is an optical sensor, and theoptical sensor outputs at least one pulse per one motor revolution.

A color wheel assembly according to a 4th aspect of the presentinvention comprises a color wheel which is divided into plural colorregions, and a motor for rotating the color wheel, in which the motorand the color wheel are aligned with each other, and a sensor which isprovided inside the motor outputs at least one pulse per one motorrevolution at designated color switching of the color wheel.

According to a 5th aspect of the present invention, in the color wheelassembly of the 4th aspect, the alignment between the motor and thecolor wheel is carried out by putting a common pin into a positioninghole which is previously formed on the color wheel and a positioninghole which is previously formed on a rotor as a rotating part of themotor.

According to a 6th aspect of the present invention, in the color wheelassembly of the 4th aspect, the alignment between the motor and thecolor wheel is carried out by putting in a common key in a positioningkeyway which is previously formed on the color wheel and a positioningkeyway which is previously formed on a rotor as a rotating part of themotor.

According to a 7th aspect of the present invention, in the color wheelassembly of the 1st or 4th aspect, the sensor which is provided insidethe motor is configured to be movable in the motor so that the positionof the sensor can be finely adjusted in a peripheral direction of themotor.

A field sequential color display device according to an 8th aspect ofthe present invention includes a color wheel assembly comprising: acolor wheel which is divided into plural color regions; and a motor forrotating the color wheel, in which the motor contains a sensor fordetecting rotation of the motor, the sensor outputs at least one pulseper one motor revolution, and a spatial light modulator for displayingimage data is driven in synchronization with the pulse which is outputby the sensor.

A field sequential color display device according to a 9th aspect of thepresent invention includes a color wheel assembly comprising: a colorwheel which is divided into plural color regions; and a motor forrotating the color wheel, in which the motor and the color wheel arealigned to each other, and a sensor which is provided inside the motoroutputs at least one pulse per one motor revolution at designated colorswitching of the color wheel, and a spatial light modulator fordisplaying image data is driven in synchronization with the pulse whichis output by the sensor.

A field sequential color display device according to a 10th aspect ofthe present invention includes a color wheel assembly comprising: acolor wheel which is divided into plural color regions; and a motor forrotating the color wheel, in which the motor contains a sensor fordetecting rotation of the motor, the sensor outputs at least one pulseper one motor revolution, and a spatial light modulator for displayingimage data is driven in synchronization with a pulse which is obtainedby electrically shifting the phase of the pulse output by the sensorforward or backward.

A field sequential color display device according to an 11th aspect ofthe present invention includes a color wheel assembly comprising: acolor wheel which is divided into plural color regions; and a motor forrotating the color wheel, in which the motor and the color wheel arealigned with each other, a sensor which is provided inside the motoroutputs at least one pulse per one motor revolution at designated colorswitching of the color wheel, and a spatial light modulator fordisplaying image data is driven in synchronization with a pulse which isobtained by electrically shifting the phase of the pulse output by thesensor forward or backward.

A color wheel unit according to a 12th aspect of the present inventioncomprises: a color wheel which is divided into plural color regions; amotor for rotating the color wheel; and a color wheel case for housingthe color wheel and the motor, in which an outer surface of the colorwheel case has a radiating means having plural projections anddepressions formed.

A color wheel unit according to a 13th aspect of the present inventioncomprises: a color wheel which is divided into plural color regions; amotor for rotating the color wheel; and a color wheel case for housingthe color wheel and the motor, in which an outer surface of the motorhas a radiating means having plural projections and depressions formed.

A color wheel unit according to a 14th aspect of the present inventioncomprises: a color wheel which is divided into plural color regions; amotor for rotating the color wheel; and a color wheel case for housingthe color wheel and the motor, in which the color wheel case has ahollow structure which is filled with a liquid.

According to a 15th aspect of the present invention, in the color wheelunit of the 14th aspect, the color wheel case has a liquid inlet and aliquid outlet, and the liquid is injected into the liquid inlet anddischarged from the liquid outlet, thereby circulating the liquid in thecolor wheel case.

A color wheel unit according to a 16th aspect of the present inventioncomprises: a color wheel which is divided into plural color regions; amotor for rotating the color wheel; and a color wheel case for housingthe color wheel and the motor, in which a light incident/radiating partof the color wheel case is sealed with a light-transmittable member.

According to a 17th aspect of the present invention, in the color wheelunit of the 16th aspect, the light-transmittable member is coated by ananti-reflection coating at least on one side thereof.

According to an 18th aspect of the present invention, in the color wheelunit of the 16th aspect, the light-transmittable member is coated by anultraviolet-reflection coating at least on one side thereof.

According to a 19th aspect of the present invention, In the color wheelunit of the 16th aspect, the light-transmittable member is anultraviolet-absorbing glass pane.

According to a 20th aspect of the present invention, in the color wheelunit of the 16th aspect, the light-transmittable member is coated by aheat-reflecting coating at least on one side thereof.

According to a 21st aspect of the present invention, in the color wheelunit of the 16th aspect, the light-transmittable member is aheat-absorbing glass pane.

According to a 22nd aspect of the present invention, in the color wheelunit of the 16th aspect, the light-transmittable member is a transparentlens.

A color wheel unit according to a 23rd aspect of the present inventioncomprises: a color wheel which is divided into plural color regions; amotor for rotating the color wheel; and a color wheel case for housingthe color wheel and the motor, in which a cushioning material isinserted at a junction of the color wheel case.

A color wheel unit according to a 24th aspect of the present inventioncomprises: a color wheel which is divided into plural color regions; amotor for rotating the color wheel; and a color wheel case for housingthe color wheel and the motor, in which a cushioning material isinserted at a junction between the color wheel case and the motor.

According to a 25th aspect of the present invention, in the color wheelunit of the 23rd or 24th aspect, the cushioning material is an O-ring,which is provided completely around the junction of the color wheel casewhich is divided into two.

A color wheel unit according to a 26th aspect of the present inventioncomprises; a color wheel which is divided into plural color regions; amotor for rotating the color wheel; and a color wheel case for housingthe color wheel and the motor, in which a cushioning material isinserted at a fixing part for installing the color wheel case on achassis.

A field sequential color display device according to a 27th aspect ofthe present invention comprises: a light source; a condensing means forcondensing light emitted from the light source; a color wheel unitcomprising a color wheel which is divided into red, green and blueregions, a motor for rotating the color wheel, and a color wheel casefor housing the color wheel and the motor, and selectively transmittingor reflecting light of red, green and blue bands in a predeterminedorder, out of the light which has been condensed by the condensingmeans; an illuminating means for condensing the light which has beentransmitted or reflected by the color wheel unit, and illuminating aspatial light modulator; a spatial light modulator for modulating thelight incident from the illuminating means; and a projection means forprojecting the light modulated by the spatial light modulator on ascreen, in which the color wheel unit is air-cooled by a fan, and aradiating means having projections and depressions formed thereon isprovided on an outer surface of the color wheel case or an outer surfaceof the motor.

A field sequential color display device according to a 28th aspect ofthe present invention comprises: a light source; a condensing means forcondensing light emitted from the light source; a color wheel unitcomprising a color wheel which is divided into red, green and blueregions, a motor for rotating the color wheel, and a color wheel casefor housing the color wheel and the motor, and selectively transmittingor reflecting light of red, green and blue bands in a predeterminedorder, out of the light which has been condensed by the condensingmeans; an illumination means for condensing the light which hastransmitted or reflected by the color wheel unit, and illuminating aspatial light modulator; a spatial light modulator for modulating thelight incident from the illumination means; and a projection means forprojecting the light which has been modulated by the spatial lightmodulator on a screen, in which the color wheel unit is used air-cooledby a fans and the color wheel case has a hollow structure, which isfilled with a liquid.

A field sequential color display device according to a 29th aspect ofthe present invention comprises: a light source; a condensing means forcondensing light emitted from the light source; a color wheel unitcomprising a color wheel which is divided into red, green and blueregions, a motor for rotating the color wheel, and a color wheel casefor housing the color wheel and the motor, and selectively transmittingor reflecting light of red, green and blue bands in a predeterminedorder, out of the light which has been condensed by the condensingmeans; an illumination means for condensing the light which has beentransmitted or reflected by the color wheel unit, and illuminating aspatial light modulator; a spatial light modulator for modulating thelight incident from the illumination means; and a projection means forprojecting the light which has been modulated by the spatial lightmodulator on a screen, in which the color wheel unit is air-cooled by afan, and a light incident/radiating part of the color wheel case issealed with a light-transmittable member.

A field sequential color display device according to a 30th aspect ofthe present invention comprises: a light source; a condensing means forcondensing light emitted from the light source; a color wheel unitcomprising a color wheel which is divided into red, green and blueregions, a motor for rotating the color wheel, and a color wheel casefor housing the color wheel and the motor, and selectively transmittingor reflecting light of red, green and blue bands in a predeterminedorder, out of the light which has been condensed by the condensingmeans; an illumination means for condensing the light which has beentransmitted or reflected by the color wheel unit, and illuminating aspatial light modulator; a spatial light modulator for modulating thelight incident from the illumination means; and a projection means forprojecting the light which has been modulated by the spatial lightmodulator on a screen, in which the color wheel unit is air-cooled by afan, and a cushioning material is inserted at a junction of the colorwheel case, a junction between the color wheel case and the motor, or afixing part for installing the color wheel case on a chassis.

A field sequential color display device according to a 31st aspect ofthe present invention comprises: a light source; a condensing means forcondensing light emitted from the light source; a color wheel unitcomprising a color wheel which is divided into red, green and blueregions, a motor for rotating the color wheel, and a color wheel casefor housing the color wheel and the motor, and selectively transmittingor reflecting light of red, green and blue bands in a predeterminedorder, out of the light which has been condensed by the condensingmeans; an illumination means for condensing the light which has beentransmitted or reflected by the color wheel unit, and illuminating aspatial light modulator; a spatial light modulator for modulating thelight incident from the illumination means; and a projection means forprojecting the light which has been modulated by the spatial lightmodulator on a screen, in which an envelope which is filled with aliquid is provided between the light source and the illumination means,and the color wheel unit is positioned in the envelope, and a radiatingmeans having plural projections and depressions formed thereon isprovided on an outer surface of the color wheel case or an outer surfaceof the motor.

A field sequential color display device according to a 32nd aspect ofthe present invention comprises: a light source; a condensing means forcondensing light emitted from the light source; a color wheel unitcomprising a color wheel which is divided into red, green and blueregions; a motor for rotating the color wheel; and a color wheel casefor housing the color wheel and the motor, and selectively transmittingor reflecting light of red, green and blue bands in a predeterminedorder, out of the light which has been condensed by the condensingmeans; an illumination means for condensing the light which has beentransmitted or reflected by the color wheel unit, and illuminating aspatial light modulator; a spatial light modulator for modulating thelight incident from the illumination means; and a projection means forprojecting the light which has been modulated by the spatial lightmodulator on a screen, in which an envelope which is filled with aliquid is provided between the light source and the illumination means,and the color wheel unit is positioned in the envelope, and the colorwheel case has a hollow structure, which is filled with a liquid.

A field sequential color display device according to a 33rd aspect ofthe present invention comprises: a light source; a condensing means forcondensing light emitted from the light source; a color wheel unitcomprising a color wheel which is divided into red, green and blueregions, a motor for rotating the color wheel, and a color wheel casefor housing the color wheel and the motor, and selectively transmittingor reflecting light of red, green and blue bands in a predeterminedorder, out of the light which has been condensed by the condensingmeans; an illumination means for condensing the light which has beentransmitted or reflected by the color wheel unit, and illuminating aspatial light modulator; a spatial light modulator for modulating thelight incident from the illumination means; and a projection means forprojecting the light which has been modulated by the spatial lightmodulator on a screen, in which an envelope which is filled with aliquid is provided between the light source and the illumination means,and the color wheel unit is positioned in the envelope, and a lightincident/radiating part of the color wheel case is sealed with alight-transmittable member.

A field sequential color display device according to a 34th aspect ofthe present invention comprises: a light source; a condensing means forcondensing light emitted from the light source; a color wheel unitcomprising a color wheel which is divided into red, green and blueregions, a motor for rotating the color wheel, and a color wheel casefor housing the color wheel and the motor, and selectively transmittingor reflecting light of red, green and blue bands in a predeterminedorder, out of the light which has been condensed by the condensingmeans; an illumination means for condensing the light which has beentransmitted or reflected by the color wheel unit, and illuminating aspatial light modulator; a spatial light modulator for modulating thelight incident from the illumination means; and a projection means forprojecting the light which has been modulated by the spatial lightmodulator on a screen, in which an envelope which is filled with aliquid is provided between the light source and the illumination means,and the color wheel unit is positioned in the envelope, and a cushioningmaterial is inserted at a junction of the color wheel case, a junctionbetween the color wheel case and the motor, or a fixing part forinstalling the color wheel case on a chassis.

A field sequential color display device according to a 35th aspect ofthe present invention comprises: a light source; a condensing means forcondensing light emitted from the light source; a color selection meansfor selectively transmitting or reflecting light of red, green and bluebands in a predetermined order, out of the light which has beencondensed by the condensing means; an illumination means for condensingthe light which has been transmitted or reflected by the color selectionmeans, and illuminating a spatial light modulator; a spatial lightmodulator for modulating the light incident from the illumination means;a projection means for projecting the light which has been modulated bythe spatial light modulator on a screen; and a shading means for shadingpart of the light incident on the color selection means or the lightwhich has been transmitted or reflected by the color selection means,and preventing light of a different color band from that of a desiredcolor which is to be displayed on the screen, from being incident on thespatial light modulator.

According to a 36th aspect of the present invention, in the fieldsequential color display device of the 35th aspect, the shading means isconstituted by a member for shading light, and has a light transmissionpart of a predetermined size, through which the light is passed.

According to a 37th aspect of the present invention, in the fieldsequential color display device of the 36th aspect, in which the size ofthe light transmission part of the shading means varies with awavelength of the light which has been transmitted or reflected by thecolor selection means.

According to a 38th aspect of the present invention, the fieldsequential color display device of the 36th aspect comprises: a lightelimination means for eliminating part of light of a specific wavelengthband, from the light which is incident on the light transmission part ofthe shading means.

According to a 39th aspect of the present invention, in the fieldsequential color display device of the 35th aspect, the shading means ispositioned on a radiation side of the color selection means.

According to a 40th aspect of the present invention, in the fieldsequential color display device of the 35th aspect, the shading means ispositioned at a 5 mm or smaller air gap with the color selection means.

According to a 41st aspect of the present invention, in the fieldsequential color display device of the 35th aspect, the light source isan extra-high pressure mercury lamp.

According to a 42nd aspect of the present invention, in the fieldsequential color display device of the 35th aspect, the condensing meansis an ellipsoidal mirror.

According to a 43rd aspect of the present invention, in the fieldsequential color display device of the 42nd aspect, the color selectionmeans has a light transmitting surface or reflecting surface which ispositioned in the vicinity of a long focus of the ellipsoidal mirror.

According to a 44th aspect of the present invention, in the fieldsequential color display device of the 35th aspect, the color selectionmeans is a color wheel comprising fan-shaped red, green and blue colorfilters which are positioned in the form of a disk, and successivelytransmits light of the respective color bands by rotating the colorwheel.

According to a 45th aspect of the present invention, in the fieldsequential color display device of the 44th aspect, the shading meansshades part of incident light with respect to a rotational direction ofthe color wheel, but does not shade the light with respect to a radialdirection of the color wheel.

According to a 46th aspect of the present invention, in the fieldsequential color display device of the 45th aspect, the shading means isa diaphragm having an opening of a predetermined size, through which theincident light is passed, an opening width of the diaphragm with respectto the rotational direction of the color wheel is set to be equivalentto or smaller than a diameter of a condensation spot which is formed onthe color wheel in an initial stage of use of the light source, and anopening width of the diaphragm with respect to the radial direction ofthe color wheel is set to be larger than the diameter of thecondensation spot.

According to a 47th aspect of the present invention, in the fieldsequential color display device of the 35th aspect, a plane orthogonalto an optical axis of the shading means is approximately circular incross section.

According to a 48th aspect of the present invention, in the fieldsequential color display device of the 47th aspect, the shading means isapproximately columnar.

According to a 49th aspect of the present invention, in the fieldsequential color display device of the 47th aspect, the shading means isapproximately conical.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram schematically illustrating an example of a colorwheel assembly according to a first embodiment of the present invention.

FIG. 2 is a cross-sectional view illustrating the color wheel assemblyaccording to the first embodiment.

FIG. 3 is a diagram schematically illustrating an example of a colorwheel assembly according to a second embodiment of the presentinvention.

FIG. 4 is a diagram schematically illustrating an example of a colorwheel assembly according to a third embodiment of the present invention.

FIG. 5 is a diagram schematically illustrating an example of a colorwheel assembly according to a fourth embodiment of the presentinvention.

FIG. 6 is a block diagram illustrating a structure if a fieldsequential-color display device using a color wheel according to a fifthembodiment of the present invention.

FIG. 7 is a diagram schematically illustrating an example of a colorwheel unit according to a sixth embodiment of the present invention.

FIG. 8 is a cross-sectional view illustrating an example of a colorwheel unit according to a seventh embodiment of the present invention.

FIG. 9 is an exploded view illustrating an example of a color wheel unitaccording to an eighth embodiment of the present invention.

FIG. 10 is a diagram schematically illustrating an example of a colorwheel unit according to a ninth embodiment of the present invention.

FIG. 11 is a cross-sectional view illustrating an example of a colorwheel unit according to a tenth embodiment of the present invention.

FIG. 12 is a cross-sectional view illustrating an example of a colorwheel unit according to an eleventh embodiment of the present invention.

FIG. 13 is a cross-sectional view illustrating an example of a colorwheel unit according to a twelfth embodiment of the present invention.

FIG. 14 is a cross-sectional view illustrating an example of a colorwheel unit according to a thirteenth embodiment of the presentinvention.

FIG. 15 is a diagram schematically illustrating an example of a colorwheel unit according to a fourteenth embodiment of the presentinvention.

FIG. 16 is a diagram schematically illustrating an example of a colorwheel unit according to a fifteenth embodiment of the present invention.

FIG. 17 is a diagram schematically illustrating an example of a colorwheel unit according to a sixteenth embodiment of the present invention.

FIG. 18 is a diagram schematically illustrating an example of a colorwheel according to a seventeenth embodiment of the present invention.

FIG. 19 is a schematic diagram and a cross-sectional view illustratingan example of a color wheel according to an eighteenth embodiment of thepresent invention.

FIG. 20 is a cross-sectional view illustrating an example of a colorwheel according to a nineteenth embodiment of the present invention.

FIG. 21 is a diagram schematically illustrating an example of a colorwheel according to a twentieth embodiment of the present invention.

FIG. 22 is a diagram illustrating a structure of a field sequentialcolor display device according to a twenty-first embodiment of thepresent invention.

FIG. 23 is a diagram illustrating a structure of a field sequentialcolor display device according to a twenty-second embodiment of thepresent invention.

FIG. 24 is a diagram illustrating a structure of a field sequentialcolor display device according to a twenty-third embodiment of thepresent invention.

FIG. 25 is a front view illustrating a color wheel in FIG. 24.

FIG. 26 is a diagram for explaining the relationship between a colorwheel and a condensation spot, seen from the light incident sideaccording to the twenty-third embodiment.

FIG. 27 is a diagram for explaining the relationship between the colorwheel and the condensation spot, seen from the light incident sideaccording to the twenty-third embodiment.

FIG. 28 is a diagram for explaining the relationship among the colorwheel, the condensation spot and a flare diaphragm, seen from the lightradiating side according to the twenty-third embodiment.

FIG. 29 is a diagram for explaining the relationship among the colorwheel, the condensation spot and the flare diaphragm, seen from thelight radiating side according to the twenty-third embodiment.

FIG. 30 is a diagram illustrating a structure of a field sequentialcolor display device according to a twenty-fourth embodiment of thepresent invention.

FIG. 31 is a front view illustrating a flare diaphragm in FIG. 30.

FIG. 32 is a diagram illustrating a structure of a field sequentialcolor display device according to a twenty-fifth embodiment of thepresent invention.

FIG. 33 is an exploded perspective view illustrating a color wheel unitin FIG. 32.

FIG. 34 is a diagram illustrating a structure of afield sequential colordisplay device according to a twenty-sixth embodiment of the presentinvention.

FIG. 35 is a front view illustrating a flare diaphragm in FIG. 34.

FIG. 36 is a diagram illustrating a structure of a prior art fieldsequential color display device.

FIG. 37 is a diagram for explaining a prior art color wheel assembly.

FIG. 38 is a diagram for explaining the relationship between a colorwheel and a condensation spot in the prior art field sequential colordisplay device.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[Embodiment 1]

Hereinafter, a color wheel assembly according to the first embodiment ofthe present invention will be described with reference to FIGS. 1 and 2.

FIG. 1 is a diagram schematically illustrating an example of the colorwheel assembly of the first embodiment. As shown in FIG. 1, the colorwheel assembly of the first embodiment is constituted by a color wheel 1and a motor 2.

The color wheel 1 comprises red (R), green (G) and blue (B) colorfilters 3 r, 3 g and 3 b, which are sandwiched and fixed by hubs 4 and 5on opposing sides.

Each of the color filters 3 r, 3 g, and 3 b is a glass pane of athickness of 1 mm, and its outside shape is processed approximately inthe form of a fan having a 60°-interior angle. An optical thin film iscoated on these color filters 3 r, 3 g and 3 b, respectively, on thesurface of the glass pane, such that transmitted white light ismodulated into light of R, G and B, respectively, and two filters foreach color, i.e., 6 filters in total, are prepared.

The hubs 4 and 5 which are made of aluminum are each in the form ofdisk. The hub 4 has an opening at its the center, and these hubs 4 and 5are joined by the motor 2 and a clamper 9 (see FIG. 2).

The color filters 3 r, 3 g and 3 b are fixed by the hubs 4 and 5 in thisway. When the hub 4 is positioned so that a surface on which a wall 5 bis formed faces upward, the color filters 3 r, 3 g and 3 b are mountedsuch that the same color filters face each other across the centerengaging against the wall 5 b. Then, the hub 5 is put on the colorfilters 3 r, 3 g and 3 b, and fixed to the hub 4 with an adhesive orscrews, whereby the color filters 3 r, 3 g and 3 b are sandwiched by thehubs 4 and 5.

The motor 2 is, for example, a ball bearing type DC brushless motor, andcomprises a rotor part 6 including a ball bearing, an axis, a coil, amagnet and the like, and a bracket part 7 which covers the rotor part 6.A drive signal is given from outside the motor 2 through a lead 8,thereby rotating the rotor part 6 at a predetermined rpm. As a matter ofcourse, the color wheel 1 which is joined with the rotor part 6 rotatetogether.

FIG. 2 is a cross-sectional view illustrating an example of the colorwheel assembly according to the first embodiment. The description isgiven taking a case where the motor 2 is an outer-rotor-shaped brushlessDC motor as an example.

The motor 2 is constituted mainly by the rotor part 6 and the bracketpart 7. The rotor part 6 is a rotating part, which is fixed by bearings23 using a shaft 22 as an axis. By passing a current through a coil 24,a torque is generated by the interaction of the rotor part 6 with apermanent magnet 25.

In the bracket part 7, a Hall IC 27 is installed as a magnetic sensor.Every time a detecting magnet 28 mounted on the rotor part 6 rotates andpasses through the Hall IC 27, a pulse signal is generated bymagnetoelectric conversion characteristics of the Hall IC 27.

The Hall IC 27 is a hybrid of a Hall element and a waveform shaping IC,while it can be only a Hall element. In this first embodiment, athree-terminal Hall IC is, for example, used as the Hall IC 27, and byproviding a DC 5V power supply, it outputs a Low signal when detectingthe magnet 28 and otherwise outputs a High signal.

As described above, the Hall IC 27 as the magnetic sensor is providedinside the motor 2, and a pulse signal is generated by themagnetoelectric conversion characteristics of the Hall IC 27 every timethe detecting magnet 28 which is installed in the rotor part 6 rotatesand passes through the Hall IC 27 as the magnetic sensor, whereby thepulse signal for detecting the position of the color wheel 1 can begenerated only by the color wheel 1 and the motor 2 for rotating thecolor wheel.

Further, when the magnetic sensor is provided inside the motor 2, it isnot required to paste the aluminum tape as the index mark on the colorwheel 1, and accordingly, a position detection signal can be obtainedstably also at high-speed rotation or at elevated temperatures.

Further, when the magnetic sensor is provided inside the motor 2, evenwhen the color wheel is provided in a case to protect it against dust,it does not interfere with air currents in the case, thereby preventingthe occurrence of noise.

Further, when the magnetic sensor is provided inside the motor 2, it isnot required to provide a hub area through which light is not directlytransmitted, whereby the diameter of the color wheel can be reduced andminiaturized.

In this first embodiment, the magnetic sensor is used as the sensor,while this sensor can be an optical sensor and, for example, areflective photo-sensor can be used. In this case, the Hall IC 27 shownin FIG. 2 is replaced with a reflective photo-sensor, and the detectingmagnet 28 is replaced with aluminum tape from which light is reflected.Further, in place of pasting an aluminum tape, it is possible that partof the rotor part side of the motor has a shiny reflecting surface, andthe remaining part has a black surface which absorbs light or a grainedsurface which causes light to scatter. On the contrary, it is alsopossible that part of the rotor part side of the motor has a blacksurface which absorbs light or a grained surface which causes light toscatter, and the remaining part has a shiny surface from which light isreflected.

In this first embodiment, the outer-rotor-shaped brushless DC motor isused as the motor 2 as an example, while the shape of the motor is notrestricted to this.

[Embodiment 2]

When a color wheel assembly according to the present invention is to beused in a field sequential color display device, the positionalrelationship between the color wheel and the motor is significantlyimportant. A pulse signal is generated from the motor as in theabove-mentioned first embodiment, then the pulse signal is compared witha reference signal to control the speed and phase of the motor, and thecolor switching of the filters of the color wheel in the fieldsequential color display device is made to be driven according to thecolor of light which is modulated by the SLM. Accordingly, in order tooutput the pulse signal at a predetermined color switching, the mountingof the color wheel and the motor should be univocally decided. Besides,it is preferable that their initially adjusted states should bemaintained.

Hereinafter, a color wheel assembly according to the second embodimentis described with reference to FIG. 3.

FIG. 3 is a diagram schematically illustrating an example of the colorwheel assembly of the second embodiment. The color wheel assembly of thesecond embodiment is different from the color wheel assembly of theaforementioned first embodiment only in that it positions a color wheeland a motor. The same reference numerals as those in the firstembodiment denote the same or corresponding elements.

The color wheel assembly of the second embodiment is constituted by acolor wheel 31 and a motor 32.

The color wheel 31 comprises red (R), green (G) and blue (B) colorfilters 3 r, 3 g and 3 b, which are sandwiched and fixed by hubs 34 and35 on opposing sides. Positioning holes 36 and 38 are provided at theperiphery of an opening of the hub 34 of the color wheel 31, connectedwith the motor 32, and a rotor part 37 of the motor 32, respectively.

The positioning of the color wheel 31 and the motor 32 is carried out byaligning the positioning hole 36 which is provided at the periphery ofthe opening at the center of the hub 34 of the color wheel 31, connectedwith the motor 32, and the positioning hole 38 which is provided at therotor part 37 of the motor 32, and then press-fitting a pin 39 in theholes to tix the color wheel and the motor. It is more desirable thatthe color wheel 31 and the motor 32 are thereafter fixed further using adamper or the like.

As described above, when the common positioning pin 39 is plugged intothe positioning hole 36 which is previously formed in the color wheel 31and the positioning hole 38 which is previously formed in the rotor part37 as the rotating part of the motor 32, the effects of the color wheelassembly of the first embodiment can be obtained, as well as thepositioning of the color wheel 31 and the motor 32 can be easily carriedout, and the decided states can also be maintained at the high-speedrotation of the motor 32.

[Embodiment 3]

Hereinafter, a color wheel assembly according to the third embodiment ofthe present invention will be described with reference to FIG. 4.

FIG. 4 is a diagram schematically illustrating an example of the colorwheel assembly of the third embodiment. The color wheel assembly of thethird embodiment is different from the color wheel assembly of the firstembodiment only in that it positions a color wheel and a motor. The samereference numerals as those in the first embodiment denote the same orcorresponding elements.

The color wheel assembly of the third embodiment is constituted by acolor wheel 41 and a motor 42.

The color wheel 41 comprises red (R), green (G) and blue (B) colorfilters 3 r, 3 g and 3 b, which are sandwiched and fixed by hubs 44 and45 on opposing sides. Further, keyways 46 and 48 are provided at theperiphery of an opening of the hub 44 of the color wheel 41, connectedwith the motor, and a rotor part 47 of the motor 42, respectively.

The positioning of the color wheel 41 and the motor 42 is carried out byaligning the keyway 46 which is provided at the periphery of the openingat the center of the hub 44 of the color wheel 41, connected with themotor 42, with the keyway 48 which is provided at the rotor part of themotor 42, and press-fitting a key 49 in the keyways 46 and 48 to fix thecolor wheel 41 and the motor 42. It is more desirable that the colorwheel 41 and the motor 42 are thereafter further fixed using a damper orthe like.

As described above, when the keyway 46 which is previously formed on thecolor wheel 41 and the keyway 48 which is previously formed on the rotorpart 47 as the rotating part of the motor 42 are aligned with eachother, and the key 49 is press-fitted therein to fix the color wheel 41and the motor 42, the effects of the color wheel assembly of the firstembodiment are obtained, as well as allowing the color wheel 41 and themotor 42 to be easily aligned, and the decided state can also bemaintained at the high-speed rotation of the motor.

In the aforementioned second and third embodiments, two simple andhighly useful two methods are described, while the method forpositioning the color wheel and the motor is not restricted to these. Aslong as the motor and the color wheel are previously aligned with eachother, and at least one pulse per one revolution is output at adesignated color switching from the Hall element which is providedinside the motor, any method can be used for positioning the color wheeland the motor, for example by aligning the color wheel and the motor bycombining a pair of a bump and a dip, by combining numerous bumps anddips like a gear, or by using a clamper.

[Embodiment 4]

Hereinafter, a color wheel assembly according to the fourth embodimentof the present invention will be described with reference to FIG. 5.

FIG. 5 is a diagram schematically illustrating an example of the colorwheel assembly of the fourth embodiment. The color wheel assembly of thefourth embodiment is different from the color wheel assembly of thefirst embodiment only in that it can shift a phase of a pulse signalwhich is mechanically output from the motor after the positioning of thecolor wheel and the motor, slightly forward or backward. The samereference numerals as those in the first embodiment denote the same orcorresponding elements.

The color wheel assembly of the fourth embodiment is constituted by acolor wheel 51 and a motor 52.

A back lever 53 of the motor 52, which is mounted on the color wheel 51,is direct-coupled to a sensor (not shown), and when the lever 53 ismoved in parallel to the motor periphery, the sensor is similarly movedslightly. The rotational direction of the color wheel is shown by anarrow in the figure. When the lever 53 is moved slightly in the samedirection as the rotational direction of the color wheel, the phase isshifted backward. When the lever 53 is moved slightly in the oppositedirection to the rotational direction of the color wheel, the phase isshifted forward.

As described above, by providing the lever 53 for slightly moving thesensor which is provided inside the motor 52, even when the colorswitching of the filter and the positional relationship of the sensorare slightly deviated, resulting from an error in the processingprecision of the color wheel 51 or the motor 52, this can bemechanically compensated.

[Embodiment 5]

Hereinafter, a field sequential color display device according to thefifth embodiment of the present invention will be described withreference to FIG. 6.

FIG. 6 is a block diagram illustrating a structure of the fieldsequential color display device of the fifth embodiment.

As shown in FIG. 6, the field sequential color display device of thefifth embodiment comprises a signal interface 61, a pixel data processor62, a display memory 63, a SLM 64, a color wheel assembly 65, and amotor controller 66.

The signal interface 61 can receive various types of input signals, andassume here that the input signal is a standard video signal havinghorizontal and vertical synchronous components. As described below, thevertical synchronous signal is used as a reference signal for adjustingthe speed of the color wheel assembly 65. The input signal can begraphics data of a PC or the like, and the reference signal can be theone which is obtained from another signal source.

The pixel data processor 62 performs various processing tasks, therebypreparing data which are to be displayed on the SLM 64. The dataprocessor includes a processing memory which stores data at theprocessing. The process which is performed by the data processor includedegamma correction, color space conversion, and interlace interpolation.In the degamma correction, influences of gamma correction performed forbroadcast signals are eliminated, and nonlinear movement of a CRT iscompensated. In the color space conversion, the data are converted intoRGB data. The interlace interpolation is used for converting aninterface data field into a complete frame, by generating new data formeeting an odd or even line. These processes are carried out in anyorder.

The display memory 63 receives pixel data which have been processed bythe data processor 62. The display memory 63 formats the data in a“bit-plane” format on the input or output, and supplies the bit-plane tothe SLM 64. According to the bit-plane format, one bit is supplied atone time for each pixel of the SLM 64, and each pixel is turned on oroff according to the bit value. For example, when each pixel isrepresented by 8 bits for each of three colors, a frame exists every 3×8bit, i.e., 24-bit plane. In typical display systems, the memory is adouble-buffer memory, which means that it has a capacity for at leasttwo display frames. Data in a buffer for one display frame are read outto the SLM 64, while data are written into a buffer for another displayframe. These two buffers are alternately controlled so that data arecontinuously read to the SLM 64.

The SLM 64 is a spatial light modulator, such as a LCOS and a DMD(Digital Micromirror Device).

The color wheel assembly 65 is the color wheel assembly described in anyof the aforementioned first to fourth embodiments, and is constituted bya color wheel comprising plural color filters and a motor for rotatingthis color wheel. A sensor for detecting the rotation of the motor iscontained by the motor, and one pulse is output per one motorrevolution.

In this fifth embodiment, one pulse is output per one motor revolution,while the same effects can be obtained as long as at least one pulse isoutput per one motor revolution.

The motor controller 66 detects the rotation speed and position of thecolor wheel on the basis of the pulse signal which is output from thecolor wheel assembly 65, and outputs a drive signal to the motor of thecolor wheel assembly 65 so as to be synchronized with the referencesignal (of predetermined rpm and phase) as the vertical synchronoussignal which is output from the signal interface 61, thereby controllingthe rotation speed and phase of the color wheel. For example, therotation speed is controlled so that the number of revolutions of themotor becomes 60 revolutions per second, to correspond to the displayspeed of 60 frames per second. Further, the phase is controlled byaccelerating or decelerating the speed of the motor of the color wheelassembly 65, so that light passing through the color wheel correspondsto data which are displayed by the SLM 64.

The operation of the so-constructed field sequential color displaydevice is described.

White light emitted from a lamp such as a discharging-type high outputlamp, for example, a xenon lamp, a metal halide lamp, or an extra-highpressure mercury lamp, which is positioned to condense light beams onthe color wheel of the color wheel assembly 65 is sent to the SLM 64through the color wheel of the color wheel assembly 65. The color wheelassembly 65 has a color wheel comprising red, blue and green colorfilters which are arranged in the form of a disk, and in synchronizationwith filtering of a light beam by each of the filters, the SLM 64displays an image frame of the color of the beam. Normally, the colorwheel of the color wheel assembly 65 is rotated by the motor onerevolution per image frame in 1/60 sec, or at 3600 rpm. In this fieldsequential color display device, there are six sub-frames during oneframe frequency, the respective being red, green, blue, red, green, andblue. The SLM 64 switches display images for the respective colors at aconsiderably high speed, and modulated respective color beams areenlargedly displayed on a screen using a projection lens. Videos of therespective colors R, G, B, R, G and B are successively displayed on thescreen in 1/60 sec, so that these videos are perceived by the eyes asafter-images, whereby full-color videos are recognized.

At this time, the color of the color wheel of the color wheel assembly65 should be synchronized with the video displayed by the SLM 64. Theprocess for synchronizing the color of the color wheel of the colorwheel assembly 65 and the video displayed by the SLM 64 is carried outby the motor controller 66.

The motor controller 66 initially compares a reference phase and speeddata as the reference signal which is output from the signal interface,with data which are obtained from a phase feedback signal and a speedfeedback signal as the pulse signal which is output by the motor.

This comparison gives a phase error value or speed error value. Both ofthe error values indicate how much the duty cycle of the drive signalwhich has been subjected to the pulse width modulation should beextended or reduced to accelerate or decelerate the motor. In this fifthembodiment, the reference signal is a vertical synchronous signal of thestandard television signal. The pulse is generated at a speed of about60 fields per sec, which corresponds to the speed of 60 revolutions persec of the color wheel. The synchronous pulse sets the phase, by givinga reference time, at which time a certain position on the color wheelshould be at a certain point. It is desirable that the pulse signalwhich is output from the color wheel assembly 65 should match thereference pulse.

The rotation speed of the color wheel assembly 65 becomes approximatelya desired speed during an initial motor start-up. Then, the speed errorof the pulse signal which is output from the color wheel assembly 65 foreach rotation is detected until the pulse signal matches the referencepulse for each rotation. Then, the phase is locked and while the phaseis locked, an error between the index position and the referenceposition is detected.

As described above, the color wheel assembly 65 is driven and rotated bythe motor, and the phase and the number of revolutions of the motor arecontrolled by the motor controller 66.

On the other hand, input data which have been input to the signalinterface 61 are converted by the pixel data processor 62 into a signalformat according to the time-multiplexed driving of the SLM. Further,the data are stored in the display memory, and output to the SLM at apredetermined timing.

As described above, when the color display is performed in atime-multiplexed and color sequential manner using the color wheelassembly described in any of the aforementioned first to fourthembodiments, the position of the color wheel can be detected only by thecolor wheel and the motor for rotating the color wheel.

Since the field sequential color display device can obtain a positiondetection signal stably also at highspeed rotation or at elevatedtemperatures, the process of synchronizing the color of the color filteron the color wheel with the video which is displayed by the SLM can becarried out accurately even at high-speed rotation or at elevatedtemperatures.

As examples of the field sequential color display device according tothe fifth embodiment, there are, for examples a field sequential colordisplay device using a projection lens and a direct-view-type fieldsequential color display device using an eyepiece.

[Embodiment 6]

Hereinafter, a color wheel unit according to the sixth embodiment of thepresent invention will be described with reference to FIGS. 7, 8 and 9.

FIG. 7 is a diagram schematically illustrating the color wheel unit ofthe sixth embodiment. This color wheel unit is constituted mainly by acolor wheel case lid 71, a color wheel case body 72, a color wheel (notshown), and a motor (not shown). A radiating fin part 73 and a lightincident opening 74 are formed on the color wheel case lid 71. In orderto simply describe the internal structure, a cross-sectional view of thecolor wheel unit according to the sixth embodiment is given in FIG. 8.Here, a color wheel assembly which is constituted by a color wheel 81and a motor 82 for rotating the color wheel is the color wheel assemblydescribed in any of the aforementioned first to fourth embodiments. Themotor 82 is fixed to the color wheel case body 72, and the color wheel81 is housed by the color wheel lid 71. As apparent from thecross-sectional view, the radiating fin part 73 is integrated with thecolor wheel case lid 71, and has plural narrow gather-shaped projectionsand depressions formed to efficiently dissipate heat which is conductedto the color wheel case, into the air.

FIG. 9 is an exploded view schematically illustrating the color wheelunit, with the color wheel care lid 71 being removed. The color wheelcomprises green (G), red (R) and blue (B) color filters 91, 92 and 93,which are sandwiched and fixed by two hubs 94 on opposing sides. Each ofthe color filters 91, 92 and 93 is a glass pane of 1-mm thickness, andthe outside shape thereof is processed in an approximately fan shapehaving a 60-degree interior angle. The color filters 91, 92 and 93 eachare a dichroic filter comprising a glass pane whose surface is coated byan optical thin film so that transmitted white light is modulated intolight of the respective color R, G or B, and two filters for each color,i.e., six filters in total, are prepared. Each of the hubs 94 is made ofaluminum has a disk shape, has an opening at its center, and the hubs 94are joined by a rotor of the motor and a damper 95. The color filters91, 92 and 93 are fixed by the hubs 94 in this way. Initially, the colorfilters 91, 92 and 93 are positioned on the hub so that the same colorfilters face each other across the center. Then, the other hub 94 is puton the color filters 91, 92 and 93, and fixed to the hub 94 with anadhesive or screws, whereby the color filters 91, 92 and 93 aresandwiched by the hubs 94.

The motor 82 is, for example, a ball bearing type DC brushless motor,and constituted mainly by a rotor part including a ball bearing, anaxis, a coil, a magnet and the like, and a bracket part which covers therotor part. A drive signal is received from outside the motor 82 througha lead or the like, thereby rotating the rotor part at a predeterminedrpm. Naturally, the color wheel 81 which is joined with the rotor partrotate together.

When the color wheel is housed in the color wheel case as describedabove, the radiating fin part 73 having plural projections anddepressions is provided on the color wheel case lid 71, whereby thecolor wheel case lid 71 has an increased surface area which is incontact with air, and higher heat radiation effects are realized. Fromthe foregoing, increases in the temperature of the color wheel case canbe prevented, whereby the reliability of the color wheel 81 and themotor 82 housed in the color wheel case can be increased.

In order to increase the heat radiation effects, it is preferable thatcut-ups, bumps, grooves or the like are provided on the gather-shapedradiating fin part 73 as shown in FIG. 8, to further increase thesurface area.

In addition, the color wheel case lid 71, the color wheel case body 72and the radiating fin part 73 are preferably made of high thermalconductivity metals such as brass, aluminum and copper, and it ispreferable that its surface is a reflecting surface which hardly absorbsunnecessary light.

In the present invention, the shape of the case is all columnar, whileit is needless to say that the case can have other shapes such as arectangular parallelepiped, a spherical shape, and a conical shape.

In the sixth embodiment, the side of the color wheel case lid 71 is thelight incident side. However, the reason of this is that loads imposedon the motor in terms of heat are favorably smaller, and therefore thespirit of the present invention is not changed even when the side of thecolor wheel case lid 71 is the light radiating side.

[Embodiment 7]

Hereinafter, a color wheel unit according to a seventh embodiment of thepresent invention will be described with reference to FIG. 10.

FIG. 10 is a diagram schematically illustrating the color wheel unit ofthe seventh embodiment. As shown in FIG. 10, a radiating fin part 103and a light incident opening 104 are formed on a color wheel case lid101. Though not shown, a color wheel and a motor are fixed to a colorwheel case body 102, and housed in the case. The radiating fin part ofthe color wheel unit according to the sixth embodiment is the one havingplural gather-shaped projections and depressions, while the radiatingfin part 103 of the seventh embodiment has plural columnar projectionsand depressions formed as shown in FIG. 10, thereby having higher heatradiation effects.

[Embodiment 8]

Hereinafter, a color wheel unit according to the eighth embodiment ofthe present invention will be described with reference to FIG. 11. FIG.11 is a cross-sectional view illustrating the color wheel unit of theeighth embodiment. As shown in FIG. 11, a color wheel 81 and a motor 115are housed by a color wheel case lid 111 and a color wheel case body112. The motor 115 is fixed to the color wheel case body 112, and aradiating fin part 113 is formed on a bracket part which is exposedoutside. This radiating fin part 113 is integrated with the bracket partof the motor 115, and has plural narrow gather-shaped projections anddepressions formed to efficiently dissipate heat which is conducted tothe color wheel 81 and the motor 115, into air. Especially; when themotor 115 has a bearing, a metal or oil bearing type, grease or oil isused on the shaft surface to reduce friction at the rotation, and thevolatilization or deterioration thereof is serious at elevatedtemperatures, whereby the reliability of the motor is considerablyharmed. In the color wheel unit of the eighth embodiment, to effectivelysuppress the deterioration of the motor, a radiating means having pluralprojections and depressions is provided on the outer surface of themotor, thereby realizing higher heat radiation effects.

The radiating fin part 113 shown in FIG. 11 can be a radiating fin parthaving columnar projections and depressions as shown in FIG. 10. Inaddition, the motor 115 contains a sensor for detecting the rotation ofthe motor, and outputs one pulse per one motor revolution, like themotor described in any of the aforementioned first to fourthembodiments.

[Embodiment 9]

Hereinafter, a color wheel unit according to the ninth embodiment of thepresent invention will be described with reference to FIG. 12. FIG. 12is a cross-sectional view illustrating the color wheel unit of the ninthembodiment. As shown in FIG. 12, a color wheel 81 and a motor 115 arehoused by a color wheel case lid 121 and a color wheel case body 122.The motor 115 is fixed to the color wheel case body 122, and a radiatingfin part 113 is formed on a bracket part which is exposed outside. Theradiating fin part 113 is integrated with the bracket part of the motor115, and has plural narrow gather-shaped projections and depressionsformed thereon to effectively dissipate head which is conducted to thecolor wheel 81 and the motor 115, into the air. Further, radiating finparts 123 and 124 are formed on the color wheel case lid 121 and thecolor wheel case body 122, respectively, whereby the heat radiationeffects are increased in the entire color wheel.

[Embodiment 10]

Hereinafter, a color wheel unit according to the tenth embodiment of thepresent invention will be described with reference to FIG. 13. FIG. 13is a cross-sectional view illustrating the color wheel unit of the tenthembodiment. As shown in FIG. 13, a color wheel 81 and a motor 82 arehoused by a color wheel case lid 131 and a color wheel case body 132.The motor 82 is fixed to the color wheel case body 132, and a radiatingfin part 133 is bonded on the outer surface of the color wheel case lid131 through thermal conducting grease 134. The heat radiation effectsthereof are slightly inferior to those of the radiating fin part 73which is integrated with the color wheel case lid 71 shown in FIG. 8,but this radiating fin part 133 can be easily removed.

This radiating fin part 133 can be bonded to an outer surface of thecolor wheel case body 132 and an outer exposed part of the motor 82. Thelarger the surface area is, the higher the heat radiation effects are.

[Embodiment 11]

Hereinafter, a color wheel unit according to the eleventh embodiment ofthe present invention will be described with reference to FIG. 14. FIG.14 is a cross-sectional view illustrating the color wheel unit accordingto the eleventh embodiment. As shown in FIG. 14, a color wheel 81 and amotor 115 are housed by a color wheel case lid 141 and a color wheelcase body 142. The motor 115 is fixed to the color wheel case body 142,and a radiating fin part 113 is formed on a bracket part which isexposed outside. This radiating fin part 113 is integrated with thebracket part of the motor 115, and has plural narrow gather-shapedprojections and depressions formed to efficiently dissipate heat whichis conducted to the color wheel 81 and the motor 115, into air. Thecolor wheel case lid 141 and the color wheel case body 142 each has ahollow structure, in which a coolant 143 is sealed. In this eleventhembodiment, an ethylene glycol solution is used as the coolant 143. Thecoolant which has taken heat in the vicinity of the light incidentopening or light radiating opening where increases in the temperatureare especially substantial is circulated by natural convection, wherebythe temperatures of the color wheel case lid 141 and the body 142 arehomogenized, and heat is dissipated from the entire surface into air, tocool the color wheel unit. Since it is difficult to circulate thecoolant in the vicinity of the motor 115 and the color wheel 81, theradiating fin part 113 on the exposed bracket part of the motor 115efficiently dissipates heat into the air. It goes without saying thatthe cooling effects are further increased by using the radiating finparts having plural projections and depressions together, which areprovided on the outer surfaces of the color wheel case lid 141 and thecolor wheel case body 142 as shown in the above-mentioned examples.

[Embodiment 12]

Hereinafter, a color wheel unit according to the twelfth embodiment ofthe present invention will be described with reference to FIG. 15. FIG.15 is a diagram schematically illustrating the color wheel unit of thetwelfth embodiment. A cross section of the color wheel unit is almostthe same as that shown in FIG. 14, and a color wheel case lid 151 and acolor wheel case body 152 each have a hollow structure, in which acoolant is sealed. Further, in this embodiment, this coolant is injectedto the color wheel case lid 151 and the color wheel case body 152through coolant inlets 154 and 156, respectively, circulated in thecase, and discharged to the outside through the coolant outlets 155 and157, respectively. During this time, the coolant takes heat of lightbeams which has been absorbed by the color wheel case lid 151 and thecolor wheel case body 152, thereby cooling the color wheel unit. Thoughnot shown, the coolant which has taken the heat and been warmed aredischarged through the coolant outlets 151 and 157, then naturally orforcefully cooled, and thereafter injected again into the color wheelcase lid 151 and the color wheel case body 152 through the coolantinlets 154 and 156, respectively, and circulated to cool the color wheelunit. The mounted positions, the shapes, and the number of the coolantinlets 154 and 156 and the coolant outlet 155 and 157 are not restrictedto those shown in FIG. 15.

[Embodiment 13]

Hereinafter, a color wheel unit according to the thirteenth embodimentof the present invention will be described with reference to FIG. 16.FIG. 16 is a diagram schematically illustrating the color wheel unit ofthe thirteenth embodiment. As shown in FIG. 16, a radiating fin part 163and a light incident opening 164 are formed on a color wheel case lid161. Though not shown, a color wheel and a motor are fixed to a colorwheel case body 162, and housed in the case. A circular transparentplate 165 is mounted to seal the light incident opening 164, and fixedby a keep plate 166. Even when the color wheel and the motor are housedin the case, at least an opening into or from which light beams enter oremerge is required. When this opening is left open, problems of a riskthat broken glass caused by breakage of the color filters scatters inthe device or a reduced display luminance caused by dust or dirtattracted by charged glass, cannot be sufficiently solved. Further,since the internal pressure is changed resulting from the high-speedrotation of the color wheel in the case, a large quantity of air isinjected into or discharged from this opening. Noise which is caused byself-excitation vibrations of air at this time are quite large.Especially, when the size of the light incident opening is reduced, thenoise caused by the injection or discharge of air tend to be loud.Therefore, in this embodiment, the light incident opening 164 is sealedwith the transparent plate 165 having the same shape as the opening 164,whereby the light beams are transmitted while the air flow isintercepted to suppress the noise. The keep plate 166 is open in an areawhere the beams are transmitted through, and is provided to fix thetransparent plate 165 to the color wheel case lid 161. When thetransparent plate 165 is bonded with a heat-resistant adhesive, forexamples one-liquid silicone resin adhesive, the keep plate 166 can bedispensed with. Further, though not shown in FIG. 16, the lightradiating opening should be similarly sealed with a transparent plate.In this case, the sealing of the color wheel case can be significantlyincreased, while on the contrary, the cooling becomes more difficult.Therefore, by forming the radiating fin part 163 on the outer surface ofthe color wheel case lid 161, heat in the case is more effectivelydissipated to cool the case.

In a case where the transparent plate 165 shown in FIG. 16 is a glasspane, reflection of light occurs on an interface between air and glass,resulting in about a 4% of lost of light. Since one glass pane has twointerfaces, this results in about 15% reduction in the brightness intotal, summing up reductions on the light incident side and the lightradiating side. In this embodiment, the loss in the brightness can becontrolled to about 2% or less, by covering both sides of thetransparent plate 165 on which light is incident, with areflection-inhibiting coating. Since the beams entering into or emergingfrom the transparent plate 165 are white light beams, it is preferablethat the reflection-inhibiting coating is a multi-coating comprisingplural laminated optical thin films which are obtained by evaporating ametal oxide. This certainly holds true for a transparent plate which isused for the light radiating opening (not shown).

In addition, when a glass plate which is coated with anultraviolet-reflecting film at least one side thereof is used as thetransparent plate 165 which is to be used for the light incident opening164, harmful ultraviolet rays can be eliminated before reaching thecolor wheel. Further, the adhesive which is used for fixing the colorfilters to the hub can be prevented from being deteriorated byultraviolet rays, whereby an increased reliability of the color wheel isexpected.

In addition, by using a ultraviolet-absorbing glass pane as thetransparent plate 165 which is to be used for the light incident opening164, the harmful ultraviolet rays can also be eliminated before reachingthe color wheel. Since beams which are gathered directly from the lampreach the color wheel, beams having large incident angles aretransmitted through the transparent plate 165. Because theultraviolet-absorbing film has a dependence on the incident angle,ultraviolet rays having larger incident angles are hardly reflected. Onthe other hand, since the ultraviolet-absorbing glass does not have adependence on the incident angle, a satisfactory elimination of theultraviolet rays is enabled. Accordingly, the adhesive can be preventedfrom being deteriorated by the ultraviolet rays, whereby an increasedreliability of the color wheel is expected. It is preferable to use theultraviolet-absorbing glass as the transparent plate 165 and theultraviolet-reflecting film on the light incident side.

Further, when a glass pane which is coated with a infrared-reflectingfilm at least one side thereof is used as the transparent plate 165which is to be used for the light incident opening 164, infrared rayscan be eliminated before reaching the color wheel. By reducing theinfrared rays which are reflected from the color filters, increases inthe temperature of the color wheel case can be previously prevented,whereby an increased reliability of the color wheel is expected.

Further, harmful infrared rays can also be eliminated before reachingthe color wheel by using an infrared-absorbing glass pane as thetransparent plate 165 which is to be used for the 7 light incidentopening 164. Since beams which are gathered directly from the lamp reachthe color wheel, beams having larger incident angles are transmittedthrough the transparent plate 165. At that time, because theinfrared-reflecting film has a dependence on the incident angle, theinfrared rays having larger incident angles are hardly reflected. On theother hand, since the infrared-absorbing glass does not have adependence on the incident angle, a satisfactory elimination of theinfrared rays is enabled. Accordingly, increases in the temperature canbe suppressed, whereby an increased reliability of the color wheel isexpected. It is preferable to use the infrared-absorbing glass as thetransparent plate 165 and form the infrared-reflecting film on the lightincident side.

[Embodiment 14]

Hereinafter, a color wheel unit according to the fourteenth embodimentof the present invention will be described with reference to FIG. 17.FIG. 17 is a diagram schematically illustrating the color wheel unit ofthe fourteenth embodiment. As shown in FIG. 17, a radiating fin part 173and a light incident opening 174 are formed on a color wheel case lid171. Though not shown, a color wheel and a motor are fixed to the colorwheel case body 172, and housed in the case. A circular transparentplate 175 is mounted to seal the light incident opening 174, and fixedby a keep plate 176. On the other hand, a transparent lens 177 ismounted to seal a light radiating opening (not shown), and fixed by akeep plate. The same effects as those of the color wheel unit accordingto the thirteenth embodiment as shown in FIG. 16 can be obtained in thisembodiment, while unnecessary optical components can be reduced, byusing not the transparent plate, but the transparent lens 177 especiallyon the light radiating opening. The beams emitted from the lamp aregathered and then reach the color wheel. The beams which have beensubjected to the color separation by the color wheel emerge spreadingout. It is essential to parallelize or condense these spreading beams ina later optical system and use the same, thereby increasing the lightutilization efficiency. In this embodiment, an optical design is madesuch that this condensing lens is positioned immediately behind thelight radiating opening of the color wheel case, and this transparentlens 177 is used for sealing the light radiating opening of the colorwheel case. Accordingly, a considerably high sealing of the color wheelcase can be obtained, as well as reducing the number of the opticalcomponents. On the other hand, the cooling is made more difficult, andincreases in the temperature due to heat become substantial. However, byforming the radiating fin part 173 on the outer surface of the colorwheel case lid 171, heat in the case can be dissipated more effectively,thereby cooling the inside of the case.

[Embodiment 15]

Hereinafter, a color wheel unit according to the fifteenth embodiment ofthe present invention will be described with reference to FIG. 18. FIG.18 is a diagram schematically illustrating the color wheel unit of thefifteenth embodiment. As shown in FIG. 18, a radiating fin part 183 anda light incident opening 184 are formed on a color wheel case lid 181. Alight radiating opening 186 is formed on a color wheel case body 182. Acolor wheel 185 and a motor (not shown) are fixed to the color wheelcase body 182, and housed in the case with covered by the color wheelcase lid 181. The color wheel case lid 181 and the color wheel case body182 are bonded together after the color wheel 185 and the motor arefixed to the color wheel case body 182. At that time, to prevent thecolor wheel case lid 181 from being in direct contact with the colorwheel case body 182 as well as prevent a crevice from being formed, anO-ring 187 as a cushioning material is inserted at the junction betweenthe color wheel case lid 181 and the color wheel case body 182. Thereby,an increased sealing of the color wheel case can be obtained, and evenwhen light which has been absorbed by the color wheel case lid 181 isconverted into heat, this heat is hardly conducted to the color wheelcase body 182 because the thermal conductivity of rubber or resin of theO-ring is lower than that of metal. Therefore, the conduction of heat tothe motor or color wheel which is fixed to the color wheel body 182 canbe suppressed, whereby the reliability of the color wheel and the motorcan be increased. In addition, by forming the radiating fin part 183 onthe outer surface of the color wheel case lid 181, the heat in the casecan be dissipated more effectively, thereby cooling the case. Further,since vibrations caused by the rotations of the color wheel and themotor are absorbed by the O-ring 187, noises which are caused by thevibrations at the junction between the color wheel case lid 181 and thecolor wheel case body 182 can be reduced.

[Embodiment 16]

Hereinafter, a color wheel unit according to the sixteenth embodiment ofthe present invention will be described with reference to FIG. 19. FIG.19 is a schematic diagram and a cross-sectional view illustrating thecolor wheel unit of the sixteenth embodiment. In this sixteenthembodiment, a dividing manner of the color wheel case is different fromthat described in any of the aforementioned embodiments. As shown inFIG. 19, the color wheel case lid 191 and the, color wheel case body 192are divided a the direction of a diameter of the color wheel. Aradiating f in part 193 is formed on the color wheel case lid 191, andthe radiating fin part 193, a light incident opening 194 and a lightradiating opening (not shown) are formed on the color wheel case body192. A color wheel 195 and a motor 196 are fixed to the color wheel casebody 192, and housed in the case, covered by the color wheel case lid191. The color wheel case lid 191 is kept from direct contact with thecolor wheel case body 192, and an O-ring 197 as a cushioning material isinserted at the junction between the color wheel case lid 191 and thecolor wheel case body 192 to prevent a crevice from being formed.Thereby, a better sealing of the color wheel case can be obtained. Inaddition, by forming the radiating fin part 193 on the outer surface ofthe color wheel case lid 191, heat in the case can be dissipated moreeffectively to cool the inside of the case. Further, since the O-ring197 absorbs vibrations caused by the rotations of the color wheel andthe motor, noises resulting from vibrations at the junction of the colorwheel case lid 191 and the color wheel case body 192 can be reduced.

[Embodiment 17]

Hereinafter, a color wheel unit according to the seventeenth embodimentof the present invention will be described with reference to FIG. 20.FIG. 20 is a cross-sectional view illustrating the color wheel unit ofthe seventeenth embodiment. As shown in FIG. 20, a radiating fin part203 is formed on a color wheel case lid 210. A color wheel 205 and amotor 206 are fixed to the color wheel case body 202, and housed in thecase. A cushioning material 204 is put between joint surfaces of thecolor wheel case body 202 and the motor 206, and fixed so that the colorwheel case body 202 is kept from a direct contact with the motor 206 aswell as to ensure that no crevice is formed therebetween. Thereby, anincreased sealing of the color wheel case can be obtained, and even whenlight which has been absorbed by the color wheel case lid 201 and thecolor wheel case body 202 is converted into heat, this heat is hardlyconducted to the motor 206 because the thermal conductivity of rubber orresin as the cushioning material is lower than that of metal. Therefore,the conduction of heat to the motor or color wheel can be suppressed,thereby increasing the reliability. In addition, by forming theradiating fin part 203 on the outer surface of the color wheel case lid201, the heat in the case can be dissipated more effectively, therebycooling the inside of the case. Further, since the cushioning material204 absorbs vibrations resulting from the rotations of the color wheeland the motor, noises caused by vibrations at the junction between themotor 206 and the color wheel case body 202 can be reduced.

[Embodiment 18]

A color wheel unit according to the eighteenth embodiment of the presentinvention will be described with reference to FIG. 21. FIG. 21 is adiagram schematically illustrating the color wheel unit of theeighteenth embodiment. As shown in FIG. 21, a radiating f in part 213 isformed on a color wheel case lid 211. A color wheel and a motor arefixed to a color wheel case body 212, and housed in the case. Two fixingparts for fixing the color wheel unit to an optical chassis 216 areprovided on the color wheel case. A cushioning material 215 is insertedat the fixing parts, and the color wheel unit is fixed to the opticalchassis 216, while being kept from direct contact therewith. Thecushioning material 215 is made of a vibration-isolating rubber damper.Thereby, vibrations resulting from the rotations of the color wheel andthe motor are absorbed or intercepted by the cushioning material 215,whereby noises caused by the vibrations at the junction between thecolor wheel unit and the optical chassis are reduced, and the vibrationsof the color wheel unit are not conducted to the optical chassis.Further, when the color wheel unit can be easily removed from theoptical chassis 216 like in this embodiment, the color wheel unit can beimmediately replaced and the maintenance can be easily performed if thecolor wheel should be broken or the motor should fail.

[Embodiment 19]

Hereinafter, a field sequential color display device according to thenineteenth embodiment of the present invention will be described withreference to FIG. 22. FIG. 22 is a diagram illustrating a structure ofthe field sequential color display device of the nineteenth embodiment.As shown in FIG. 22, this field sequential color display devicecomprises a color wheel unit 221, a LCOS 222, a lamp 223, a projectionlens 224, a screen 225, a cooling fan 226, and a field lens 227.

The color wheel unit 221 is the color wheel unit described in any of theseventh to eighteenth embodiments.

The LCOS 222 is one of the SLMs; and it comprises reflection pixels inthe form of a matrix formed on a silicon substrate and can switchdisplays at a high speed using a video signal.

The operation of the so-constructed field sequential color displaydevice is described. A 250 W extra-high pressure mercury lamp is used asthe lamp 223. The lamp 223 is positioned approximately in a focus pointof a concave mirror, and white light beams emitted from the lamp arecondensed by the elliptical concave mirror on the color filter of thecolor wheel. In this lamp, the luminance of the emission part is high,and emitted light beams can be efficiently condensed, Further, this lamphas good color rendering properties, and this is suitable for full-colordisplays. The color wheel comprises green, red, and blue color filters,which are positioned in the form of a disk. In synchronization withfiltering of a beam by each filter, the LCOS 222 displays an image frameof the color of the beam. In the field sequential color display deviceaccording to the nineteenth embodiment, the color wheel is rotated bythe motor two revolutions per image frame in 1/60 sec, or at 7200 rpm.In this field sequential color display device, there are twelve colorsub-frames during one frame frequency, the respective being green, red,blue, green, red, blue, green, red, blue, green, red, and blue. The LCOS222 switches the display images for the respective colors at aconsiderably high speed, and modulated beams of respective colors areenlargedly projected on the screen 225 using the projection lens 224.Since videos of the respective colors G, R, B, G, R, B, G, R, B, G, R,and B are successively displayed on the screen in 1/60 sec, these videosare perceived by the eyes being integrated as after-images, wherebyfull-color videos are recognized.

The color wheel and the motor rotate at a considerably high speed insidethe color wheel unit 221, and the color wheel unit 221 is irradiatedwith beams emitted from the lamp 223 so that the beams are condensed onthe color wheel. The concave mirror of the lamp 223 is an ellipsoidalmirror, and just over 70% of the beams are reflected from the concavemirror and condensed on the color wheel. However, nearly 30% of thebeams are not emitted toward the direction of the concave mirror, andthese beams are emitted spreading out from the front surface of theconcave mirror, whereby the color wheel unit 221 is directly radiatedwith these beams. Further, the beams which are reflected from theconcave mirror and condensed are absorbed by the color wheel case on theperiphery of the opening, when these beams pass through the lightincident opening of the color wheel unit 221. Further, beams which havebeen subjected to color separation and reflected from the color filtersof the color wheel return toward the lamp, and there are some beamswhich are absorbed inside the color wheel case. As described above, thebeams which are absorbed by the color wheel case are all converted intoheat, resulting in an increase in the temperature of the color wheelunit. Further, since the lamp itself reaches a considerably hightemperature, the temperature of the color wheel unit 221 which ispositioned in the vicinity of the lamp is also increased by theradiation heat. When the color wheel unit 221 which is under thesethermally harsh conditions is to be cooled, the radiating fin partformed on the color wheel case or the motor is cooled by the cooling fan226. Thereby, not only the color wheel case, but also the color wheeland the motor which are sealed inside the case can be sufficientlycooled. When the direction that the air is blown at that time is thesame as the orientation of the radiating fin part of the color wheelunit, higher effects can be obtained.

In this nineteenth embodiment, a projection-type display using theprojection lens is used as the field sequential color display device,while a direct-view-type field sequential color display device using aneyepiece in place of the projection lens can be used.

[Embodiment 20]

Hereinafter, a field sequential color display device according to thetwentieth embodiment of the present invention will be described withreference to FIG. 23. FIG. 23 is a diagram illustrating a structure ofthe field sequential color display device of the twentieth embodiment.As shown in FIG. 23, the field sequential color display device comprisesa color wheel unit 231, a DMD 232, a lamp 233, a projection lens 234, acooling unit 235, and a field lens 237.

The color wheel unit 231 is the color wheel unit described in any of theseventh to eighteenth embodiments.

The DMD 232 is one of the SLMs, which is a cluster of minute mirrors,and the inclination angle of each mirror can be changed by a signal toswitch the display on or off at a considerably high speed.

The operation of the so-constructed field sequential color displaydevice is described. A 150 W extra-high pressure mercury lamp is used asthe lamp 233. The lamp 233 is positioned approximately in a focus pointof a concave mirror 238, so that white light beams which are emittedfrom the lamp are condensed on the color filter of the color wheel bythe elliptical concave mirror 238. The color wheel is constituted bygreen, red, and blue color filters, which are positioned in the form ofa disk. In synchronization with filtering of the beam by each filter,the DMD 232 displays an image frame of the color of the beam. In thefield sequential color display device according to the twentiethembodiment, the color wheel is rotated by a motor three revolutions perimage frame in 1/60 sec or at 10800 rpm. In this field sequential colordisplay device, there are 18 sub-frames during one frame frequency, therespective being green, red, blue, green, red, blue, green, red, blue,green, red, blue, green, red, blue, green, red, and blue. The DMD 232switches display images for the respective colors at a considerably highspeed, and modulated beams of respective colors are enlargedly projectedon the screen using the projection lens 234. Since videos of therespective colors G, R, B, G, R, B, G, R, B, G, R, B, G, R, B, G, R andB are successively displayed on the screen in 1/60 sec, these videos areperceived by the eyes as being integrated as after-images, wherebyfull-color videos are recognized. The beams which have been subjected tothe color separation by the color wheel are made to be parallel beams bythe field lens 237, and illuminate the DMD 232 obliquely with the mirror239. In this field sequential color display device, the direction of thereflected beam is controlled according to the inclination of the mirrorwith respect to the DMD 232, and it is previously designed so that thebeam is incident on the projection lens 234 when it is ON.

The color wheel and the motor rotate at a considerably high speed insidethe motor wheel unit 231, and the color wheel unit 231 is irradiatedwith the beams emitted from the lamp 233 so that the beams are condensedon the color wheel. The cooling unit 235 is positioned in a spacebetween the concave mirror 238 of the lamp 233 and the field lens 237,and filled with a coolant 236. The color wheel unit 231 is positioned tobe immersed in the coolant 236. Since the color wheel unit 231 of thepresent invention has an excellent sealing, even when it is immersed inthe coolant, the coolant does not penetrate into the color wheel unit231.

Beams reflected from the concave mirror 238 and condensed are absorbedby the color wheel case on the periphery of the light incident openingwhen the beams pass through the opening of the color wheel unit 231.Further, beams which have been subjected to color separation andreflected from the color filter of the color wheel return toward thelamp again, and there are some beams which are absorbed inside the colorwheel case. As described above, the beams which have been absorbedinside the color wheel case are all converted into heat, therebyincreasing the temperature of the color wheel unit. Further, thetemperature of the color wheel unit 231 which is positioned in thevicinity of the lamp 233 is increased by the radiation heat. When thecolor wheel unit 231 under these thermally harsh conditions is to becooled, the radiating fin part which is especially formed on the colorwheel case or the motor is cooled by the coolant 236 in the cooling unit235. Thereby, not only the color wheel cases but also the color wheeland the motor, which are sealed in the case, can be sufficiently cooled.When the coolant 236 is circulated so as to be discharged outside of thecooling unit 235, forcefully cooled, and injected again to the coolingunit 235, the cooling effects are further increased.

In this twentieth embodiment, a projection-type display using theprojection lens is used as the field sequential color display device,while a direct-view-type field sequential color display device using aneyepiece in place of the projection lens can be used.

[Embodiment 21]

Hereinafter, a field sequential color display device according to thetwenty-first embodiment of the present invention will be described withreference to the drawings.

FIG. 24 is a diagram illustrating a structure of the field sequentialcolor display device of the twenty-first embodiment.

In FIG. 24, the field sequential color display device comprises a lamp241, an ellipsoidal mirror 242, an UV-IR cut-off filter 243, a flarediaphragm 244, a color wheel 246, a rotating motor 247, a rotationcontroller 248, a condensing lens 249, a field lens 250, atransmission-type LCD PANEL 251, a liquid crystal driver 252, and aprojection lens 253.

The lamp 241 is an extra-high pressure mercury lamp. The lamp 241 ispositioned so that the center of gravity of an emission part 241 a whichis formed between its electrodes almost matches to a first focus F1(short focus) of the ellipsoidal mirror.

The ellipsoidal mirror 242 efficiently condenses light emitted from thelamp 241 to form a condensation spot 245 at a second focus F2 (longfocus). The condensation spot 245 is a secondary light source which isequivalent to the real image of the emission part 241 a. The UV-IRcut-off filter 243 eliminates ultraviolet rays and infrared rays fromthe light emitted from the discharge lamp 241.

The flare diaphragm 244 is a conical diaphragm which is positioned onthe light radiating side of the color wheel 246, and shades part oflight which has been condensed by the ellipsoidal mirror 242 andtransmitted through the color wheel 246. Further, when a thermoplasticplastic such as PPS (polyphenylene sulfide, heat-resistant temperatureis 260° C.) is used as the material of the flare diaphragm 244, theflare diaphragm 244 can be obtained at low costs.

The color wheel 246, for example, as shown in FIG. 25, comprisesfan-shaped red, green, and blue color filters 246R, 246G, and 246B,which are combined in the form of a disk and fixed by a doughnut-shapedretainer 246 a, and is positioned so that the color wheel 246 surfacematches to the position of the second focus F2 of the ellipsoidal mirror242. The rotating motor 247 is mounted on the color wheel 246. A colorwheel assembly which is constituted by the color wheel 246 and therotating motor 247, is the color wheel assembly described in any of thefirst to fourth embodiments. The motor contains a sensor for detectingthe rotation of the motor, and outputs one pulse for one revolution ofthe motor.

The rotation controller 248 receives a video signal of each of thecolors red, green and blue, and drives the rotating motor 247 inaccordance with a synchronous signal included in the video signal, sothat light having a band of each color is transmitted through the colorwheel 246 in synchronization with the display of the LCD PANEL 251 ofeach of the colors red, blue and green. Here, to control the rotation ofthe color wheel 248, the position detection is required, and therotation controller 248 detects the rotation speed and position of thecolor wheel on the basis of a pulse signal which is output from therotating motor 247.

The condensing lens 249 is a positive power plane-convex lens, andefficiently condenses light which has been transmitted through the colorwheel 246 on the LCD PANEL 251. The field lens 250 is used forcondensing illumination light to the LCD PANEL 251 from the condensinglens 249 and guiding the light to the projection lens 253.

The LCD PANEL 251 is a ferroelectric LCOS comprising a liquid crystallayer, and a bistable device for applying voltage to the liquid crystallayer to switch between two states (ON/OFF). In the LCD PANEL 251, forexample, by exerting a PWM (pulse width modulation) control to thegradation representation, the ON time of the bistable device can bechanged, thereby changing the orientation of the liquid crystalmolecule. In addition, the LCD PANEL 251 has polarizing plates (notshown) on its incidence side and radiation side, and its polarizing axisis set according to the orientation of the liquid crystal molecule.Since the bistable device has a relatively short response time, it issuitable for cases where the color sequential display is performed bythe LCD PANEL 251, like in the present invention.

The liquid crystal driver 252 exerts the PWM (pulse width modulation)control for the LCD PANEL 251 in accordance with a video signal of red,green or blue, which is received from outside.

The projection lens 253 receives light which has been transmittedthrough the LCD PANEL 251, and enlarges an image on the LCD PANEL 251,i.e., an optical image, to enlargedly project the same on a screen (notshown).

Hereinafter, the operation of the field sequential color display deviceaccording to the twenty-first embodiment of the present invention isdescribed.

When the light emitted from the lamp 241 is condensed by the ellipsoidalmirror 242, and incident on the color wheel 246, a condensation spot 245is formed on the surface of the color wheel 246. When the respectivecolor filters 246R, 246G, and 246D pass through the condensation spot245 because of the rotation of the rotating motor 247, light beams ofred, green, and blue bands are successively transmitted through therespective color filters 246R, 246G, and 246B.

Then, the rotation controller 248 controls the rotation of the colorwheel 246 so that, for example, a period during which the LCD PANEL 251is controlled by the liquid crystal driver 252 in accordance with thevideo signal for red display is synchronized with a period during whichthe red filter 246R of the color wheel 246 is passing through thecondensation spot 245. The rotation controller 248 similarly controlsthe rotation of the color wheel 246 also when it receives other videosignals of green or blue.

When the color wheel 246 is thus rotated, and monochrome gradationdisplays of red, green and blue are switched in short periods in atime-multiplexed manner to display the same on the LCD PANEL 251, imagesdisplayed on the screen are consequently composed visually and theviewer recognizes full-colored images.

However, during a predetermined period during which the respectiveboundaries of the color filters 246R, 246G and 246B are passing throughthe condensation spot 245, the condensation spot 245 extends over twoadjacent color filters on the color wheel 246. In this case, the LCDPANEL 251 is controlled to be displayed in black, thereby preventing theoccurrence of color mixture.

FIG. 26 is a diagram for complementarily explaining the relationshipbetween the color wheel 246 and the condensation spot 245 seen from theincidence side of the color wheel 246, and the black display period ofthe LCD PANEL 251 is described with reference to this figure. FIG. 26shows an initial state of usage of the lamp 241.

When the color wheel 246 is rotated in the direction shown by an arrowin the figure, assume that a period during which the boundary 246RG ofthe red color filter and the green color filter is passing through thecondensation spot 245 is set as the black display period of the LCDPANEL 251. Also as for other boundaries 246GB and 246BR, periods whenthe boundaries are passing through the condensation spot 245 aresimilarly set as the black display period. Accordingly, the blackdisplay period of the LCD PANEL 251 is set three times per onerevolution of the color wheel 246. This black display period is setaccording to the size of the condensation spot 245 which is formed onthe color wheel 246 in the initial stage of usage of the lamp 241.

In a relatively early stage when little time has elapsed after thebeginning of use of the lamp 241, light beams which have been condensedby the ellipsoidal mirror 242 reach the color wheel 246, and thecondensation spot 245 having the size as shown in FIG. 26 is formed onthe surface of the color wheel 246. Since the period during which thecondensation spot 245 is extending over two adjacent color filters isshorter than the black display time of the LCD PANEL 251 in this stage,no color-mixed optical image is formed on the LCD PANEL 251.

On the other hand, as the lamp 241 is used for a long time, the arclength is increased in length, and the diameter of the condensation spot245 is increased in proportion to the arc length as shown in FIG. 27.Therefore, the period during which the condensation spot 245 extendsover adjacent two color filters becomes longer than the black displayperiod of the LCD PANEL 251, and accordingly a color-mixed optical imageis formed on the LCD PANEL 251.

This problem is described in more detail with reference to FIGS. 26 and27. When the condensation spot 245 is formed on the red filter 246R, theLCD PANEL 251 carried out the driving for red display. Then, immediatelybefore the boundary 246RG of the color wheel 246 reaches a start point261 a of the black display period 261, i.e., immediately before the LCDPANEL 251 carries out the black display, a part of the condensation spot245 is also in the green filter 246G area, and thus, a video in whichgreen is mixed with a red display is displayed on the LCD PANEL 251.

Then, when the boundary 246RG reaches the end point 261 b of the blackdisplay period 261, the LCD PANEL 251 finishes the black display, andthereafter immediately starts driving for green display. However, sincea part of the condensation spot 245 is also in the red filter 246R areaat that time, a video in which red is mixed with a green display isdisplayed on the LCD PANEL 251.

Also when the respective boundaries 246GB and 246BR pass through thecondensation spot 245, the LCD PANEL 251 similarly display an imagehaving blue and green mixed and an image having blue and red mixed,respectively, which are different from the colors to be normallydisplayed.

In this case, a rather long black display period can be previously seton the assumption that the arc length of the light source is increased.However, when the black display period of the LCD PANEL 251 becomeslonger, the brightness of the displayed image is undesirably reduced.

Thus, in the present invention, to solve the aforementioned problem,part of light which has been condensed by the ellipsoidal mirror 242 andtransmitted through the color wheel 246 is shaded by the flare diaphragm244, thereby preventing the size of the condensation spot 245 frombecoming larger than a desired size.

Hereinafter, the specific structure and function of the flare diaphragm244 is described with reference to FIGS. 28 and 29.

FIG. 28 is a diagram for explaining the relationship among the colorwheel 246, the condensation spot 245 and the flare diaphragm 244, seenfrom the radiation side of the color wheel 246, and shows a initialstate of use of the lamp 241.

In FIG. 29, the flare diaphragm 244 should limit the size of thecondensation spot 245 along direction of the rotation of the color wheel246. Therefore, the opening width of the flare diaphragm 244 in therotational direction of the color wheel 246 is set to be approximatelyequal to the diameter of the condensation spot 245 at the beginning ofthe use of the lamp 241. On the other hand, as for the radial directionof the color wheel 246, it is not particularly required to limit theopening width of the flare diaphragm 244, and a sufficient opening widthis given not to shade the condensation spot 245.

Here, in a relatively early stage when little time elapsed after thebeginning of use of the lamp 241, the condensation spot 245 is small asshown in FIG. 28, and light which has been transmitted through the colorwheel 246 is hardly shaded by the flare diaphragm 244, whereby the lightutilization efficiently is not significantly reduced by the flarediaphragm 244.

When the size of the condensation spot 245 becomes larger as shown inFIG. 29, light is incident on two adjacent color filters at the sametime immediately before and after the black display period of the LCDPANEL 251. However, the flare diaphragm 244 shades the light whichcauses the occurrence of the color mixture, thereby preventing theoccurrence of the color mixture in images. Besides, by using the flarediaphragm 244, the black display period of the LCD PANEL 251 can beminimized, whereby high-quality images can be obtained without impairingthe luminance of the images.

Even when the opening width of the flare diaphragm 244 in the rotationaldirection of the color wheel 246 is set smaller than the diameter of thecondensation spot 245 at the beginning of use of the lamp 241, theeffects of the present invention can be obtained. However, in this case,the light utilization efficiency is reduced according to the brightnessdistribution of the condensation spot 245.

Further, since the luminous intensity of the light which has beentransmitted through the color wheel 246 is about one-third as high asthat of the incident light, the quantity of light which is shaded by theflare diaphragm 244 positioned at the radiation side of the color wheel246 is also about one-third as large as that of the incident light.Thereby, heat generation of the flare diaphragm 244 caused by the lightis suppressed, thereby increasing the reliability of the device.

Further, since the flare diaphragm 244 is conical in shape, airresistance at the rotation of the color wheel 246 can be reduced insize, thereby suppressing noises. Here, the flare diaphragm 244 is notlimited to be conical, and any diaphragm can be used as long as a planeorthogonal to the optical axis is approximately circular in crosssection.

According to the so-constructed field sequential color display device,by providing the flare diaphragm 244, the occurrence of the colormixture in images can be prevented without setting the black displayperiod of the LCD PANEL 251 unnecessarily longer, whereby the fieldsequential color display device can realize bright and high-qualityimage displays. In addition, by positioning the flare diaphragm 244 onthe radiation side of the color wheel 246, increases in the temperatureof the flare diaphragm 244 can be suppressed, thereby increasing thereliability of the device. Further, by using the conical flare diaphragm244, noises at the rotation of the color wheel 246 can be suppressed.

[Embodiment 22]

Hereinafter, a field sequential color display device according to thetwenty-second embodiment of the present invention will be described withreference to the drawings.

FIG. 30 is a diagram illustrating a structure of the field sequentialcolor display device of the twenty-second embodiment. In this figure,the same reference numerals as those in FIG. 24 denote the same orcorresponding parts. FIG. 31 is a front view illustrating a flarediaphragm 301 in FIG. 30.

This twenty-second embodiment is different from the twenty-firstembodiment in that the size of the opening of the flare diaphragm 301can be changed in synchronization with the displaying on the LCD PANEL251.

To be more specific, as shown in FIG. 31, the flare diaphragm 301 isconstituted by a main diaphragm 301 a, moving parts 301 b, and adiaphragm controlling motor 301 c for driving the moving parts 30 1 b.

The shape of the opening of the main diaphragm 301 a is the same as thatshown in FIG. 28, and the opening width in the rotational direction ofthe color wheel 246 is set to be approximately equal to the diameter ofthe condensation spot 245 at the beginning of use of the lamp 241. Whenthe diaphragm controlling motor 301 c is driven, the moving parts 301 bare moved from positions shown by full lines 301 b″ to positions shownby broken lines 301 b′ or in the reverse direction, whereby the size ofthe opening of the flare diaphragm 301 can be adjusted.

The driving of the diaphragm controlling motor 301 c is carried out by adiaphragm controller 302 as shown in FIG. 30. The diaphragm controller302 receives a video signal of respective colors of red, blue and greenfrom an external device, then drives the diaphragm controlling motor 301c in accordance with a synchronous signal included in the video signal,and exerts a control so that image displaying on the LCD PANEL 251 issynchronized with the opening/closing of the moving parts 301 b of theflare diaphragm 301.

For example, while the LCD PANEL 251 displays video corresponding to redor blue, the moving parts 301 b of the flare diaphragm 301 are moved tothe positions shown by the broken lines 301 b′, in accordance with thedriving of the controlling motor 301 c. On the other hand, while the LCDPANEL 251 displays video corresponding to green, the moving parts 301 bare moved to the positions shown by the full lines 301 b″. Consequently,the quantity of green light which reaches the LCD PANEL 251 is reduced,whereby the white balance in the white display is changed.

When the size of the opening of the flare diaphragm 301 is adjusted asdescribed above when light of a specific color passes through the flarediaphragm 301, the white balance of the image can be arbitrarilyadjusted.

According to the so-constructed field sequential color display device,the size of the opening of the flare diaphragm 301 can be adjusted insynchronization with the video signal. Therefore, the color-mixeddisplay of the image on the LCD PANEL 251 can be prevented, and thewhite balance of the displayed image can be arbitrarily adjusted,whereby the field sequential color display device can realize bright andhigh-quality image displays.

[Embodiment 23]

Hereinafter, a field sequential color display device according to thetwenty-third embodiment of the present invention will be described withreference to the drawings.

FIG. 32 is a diagram illustrating a structure of the field sequentialcolor display device of the twenty-third embodiment. In this figure, thesame reference numerals as those in FIG. 30 denote the same orcorresponding parts, and a color wheel unit 321 is included. FIG. 33 isan exploded perspective view illustrating the color wheel unit in FIG.32.

The color wheel unit 321 is constituted by a color wheel 331, a motor333, and color wheel cases 334 and 335.

The color wheel 331 has fan-shaped red, green and blue color filters331R, 331G and 331B, which are combined in the form of a disk and fixedby a retainer 332, and is rotated by the motor 333.

The motor 333 is constituted by a rotating part 333 a and a base plate333 b. The rotating part 333 a of the motor 333 is connected to theretainer 332 of the color wheel 331, and the base plate 333 b of themotor 333 is fixed to the color wheel case 334.

The color wheel case 334 comprises an entrance window 337 having asufficient size for an optical path which is covered with translucentglass, and a flare diaphragm 336. The color wheel case 335 comprises aradiation window 338 having a sufficient size for an optical path whichis covered with translucent glass. In place of installation of the UV-IRcut-off filter 243, at least one of the translucent glass which isprovided on the entrance window 337 and the radiation window 338 of thecolor wheel cases 334 and 335 can be replaced with a filter forfiltering ultraviolet rays or infrared rays.

The flare diaphragm 336 has a diaphragm opening which protrudes towardthe inside of the color wheel case 334 so that the diaphragm opening ispositioned in the proximity of the color wheel 331. Further, theprotruding part of the flare diaphragm 336 is formed in a cylindricalshape. The flare diaphragm 336 is set to have an opening width in therotational direction of the color wheel 335, which is approximatelyequal to the diameter of the condensation spot 245 at the beginning ofuse of the lamp 241. The flare diaphragm 336 may be either formedseparately from or integrated with the color wheel case 334.

When the color wheel case 335 is fixed to the color wheel case 334, thecolor wheel 331 can be retained in a sealed space, thereby increasingthe stability at the breakage of the color wheel 331.

The light which has been condensed by the ellipsoidal mirror 242 isincident on the entrance window 337 of the color wheel case 334, and thelight which has been selectively transmitted through the color wheel 331is radiated from the radiation window 338 of the color wheel case 335.The flare diaphragm 336 has the same function as that of thetwenty-first embodiment, and it shades part of the light which isincident on the color wheel cases 334 and 335, thereby preventing thecolor mixture of images, which may be caused after a long time of use ofthe lamp 241.

In this case, the air gap between the color wheel 331 and the flarediaphragm 336 when the color wheel 331, the motor 333, and the colorwheel cases 334 and 335 are fixed to each other is set for example at 2mm. It is more preferable that the air gap between the color wheel 331and the flare diaphragm 336 is as small as possible, and when this isset at 5 mm or smaller, the shading effects can he efficiently obtained.

In addition, even when the flare diaphragm 336 is positioned in theproximity of the color wheel 331 as described above, the protrusion ofthe flare diaphragm 336 is formed in a columnar shape, and accordinglythe air resistance of the flare diaphragm 336 is small at the rotationof the color wheel 331, thereby reducing noises. The protrusion of theflare diaphragm 336 may have a shape other than the columnar shape. Thesame effects can be obtained as long as the protrusion has a shapehaving a smaller air resistance, for example, a conical shape havinginclined sides.

According to the so-constructed field sequential color display device,by sealing and retaining the color wheel 331 in the color wheel cases334 and 335 with the dare diaphragm 336, the color mixture of the imageof the LCD PANEL 251 can be prevented, and the safe performance can beimproved. Further, when the protrusion of the flare diaphragm 336 in thecolor wheel cases 334 and 335 has a shape having a relatively small airresistance, the noises can be reduced. Besides, when the air gap betweenthe color wheel 331 and the flare diaphragm 336 is 5 mm or smaller, theshading effects can be efficiently obtained.

[Embodiment 24]

Hereinafter, a field sequential color display device according to thetwenty-fourth embodiment of the present invention will be described withreference to the drawings.

FIG. 34 is a diagram illustrating a structure of the field sequentialcolor display device of the twenty-fourth embodiment. In this figure,the same reference numerals as those of FIG. 24 denote the same orcorresponding parts, and a flare diaphragm 341 is included. FIG. 35 is afront view illustrating the flare diaphragm 341 in FIG. 34.

The flare diaphragm 341 is constituted by a main diaphragm 342 and anauxiliary diaphragm 343.

The opening width of the main diaphragm 342 in the rotational directionof the color wheel 246 is set to be approximately equal to the diameterof the condensation spot 245 at the beginning of use of the lamp 241,like in FIG. 27.

The auxiliary diaphragm 343 is obtained by coating a multi-layer film343 b on a diagonally shaded area of a translucent glass 343 a. Themulti-layer film 343 b reflects on the auxiliary diaphragm 343, and themulti-layer film 343 b is evaporated so that an area where nomulti-layer film 343 b is evaporated is smaller than the opening of themain diaphragm 342.

Thereby, after the light incident on the flare diaphragm 341 has passedthrough the opening of the main diaphragm 342, part of the specificwavelength light is reflected on the multi-layer film 343 b on theauxiliary diaphragm 343, thereby reducing the quantity of passedspecific wavelength light. For example, when the multi-layer film 343 breflects only light of the green band, the light incident on the flarediaphragm 341 is radiated from the flare diaphragm 342 with reducedgreen band light.

Therefore, when the characteristics of the multi-layer film 343 b areset according to the spectrum of the light source, the white balance ofdisplayed images on the LCD PANEL 251 can be arbitrarily set.

In place of using the main diaphragm 342 as shown in FIG. 35, forexamples silver or aluminum which efficiently reflects visible radiationcan be evaporated on the plane of the translucent glass 343 a whichconstitutes the flare diaphragm 343, to form an evaporated film having afunction which is equivalent to the main diaphragm 342. In this case,the evaporated film for the main diaphragm and the multi-layer film 343b for the auxiliary diaphragm can be deposited on the same plane of thetranslucent glass 343 a, or the respective films can be formed onopposing sides of the translucent glass 343 a, respectively.

According to the so-constructed field sequential color display device,since the multi-layer film which reflects specific wavelength light isprovided on the flare diaphragm 341, the color-mixed display of theimage by the LCD PANEL 251 can be prevented, and the white balance ofthe displayed images can be arbitrarily adjusted, whereby the fieldsequential color display device which can obtain bright and high-qualityimage display can be realized.

In this embodiment, the extra-high pressure mercury lamp is used as thelamp, while a metal halide lamp, a xenon lamp or the like can be alsoused. A light source other than the discharge lamp, such as a halogenlamp and an LED, can be used.

In this twenty-fourth embodiment, the ellipsoidal mirror is used as thecondensing means for condensing the light emitted from the lamp.However, in place of the ellipsoidal minor, a parabolic mirror and apositive power lens can be combined to condense the light emitted fromthe light source. Further, parallel light reflected from the parabolicmirror can be directly used at a condensation spot.

Further, the positioning of the flare diaphragm is not particularlylimited, while color-mixed display of the image can be prevented moreefficiently in a position which is nearer to a position where thecondensation spot of the color wheel 246 is formed. To be more specific,it is more preferable to position the flare diaphragm within 5 mm of airgap from the condensation spot 245.

Further, it is preferable that the flare diaphragm has a shape whichreduces the air resistance at the rotation of the color wheel, forexample, a plane orthogonal to the optical axis is approximatelycircular in cross section.

Further, the flare diaphragm can be positioned on either the lightincident side or light radiating side of the color wheel, while it ismore preferable to position the flare diaphragm on the light radiatingside because the heat generation of the flare diaphragm can besuppressed.

Further, it is possible to use a color wheel which has reflective-typedichroic mirrors in place of the absorbing-type filters, and perform theselection of red, green, and blue band light on the basis of lightreflected from the color wheel.

Further, the color wheel is not restricted to the one which is dividedinto three, i.e., red, green, and blue filters, and a color wheel whichis divided into more than three can be used. In addition, the shape ofthe color wheel 246 is not limited to a disk shape, and any color wheelcan be used as the color selection means for implementing thisinvention, as long as the color wheel can select light of specificwavelength bands from the incident light successively in atime-multiplexed manner.

In this twenty-fourth embodiment, the ferroelectric LCOS or the DMD isused as the SLM, while a twist nematic LCOS, a LCOS which utilizesscattering of light or the like can be used as the SLM, as long as ithas a response time which enables the color sequential display.

In this embodiment, the condensing lens or field lens is used as theillumination means for illuminating the SLM, while two lens arrays orrod lens can be used in place thereof.

In this embodiment, the field sequential color display device whichperforms a front projection on a screen is described, while a fieldsequential color display device which performs a rear projection withusing a translucent screen can be constituted.

According to the color wheel assembly and the field sequential colordisplay device using the same of the present invention, the position ofthe color wheel can be detected only by the color wheel and the motorfor rotating the color wheel, whereby the position detection signal canbe obtained stably also at high-speed rotation or at elevatedtemperatures.

According to the color wheel assembly of the present invention, thecolor wheel and the motor are previously aligned, mounted, andthereafter fixed, whereby the color wheel and the motor are notdislocated. Further, a minute deviation in the precision in mounting orprocessing can be corrected by mechanical position adjustment orelectrical phase adjustment of the sensor.

According to the color wheel assembly of the present invention, it isnot required to mount a photo-sensor on the case of the color wheel,thereby preventing noises. Further, it is not required to paste an indexmark to the color wheel, whereby the space of the hub for that purposecan be eliminated, and the color wheel can be miniaturized.

According to the color wheel unit and the field sequential color displaydevice using the same of the present invention, even when the colorwheel and the motor rotate at a high speed, safety is ensured, and ifthey should be broken, the risk of scattering of glass of the filters isreduced. Further, the radiating fin part as a radiating means isprovided on the color wheel case or the motor, thereby effectivelycooling the color wheel case which is easily heated by the radiationheat from the lamp or absorption of unnecessary light, whereby thereliability of the color wheel and the motor therein can be increased.

According to the color wheel unit of the present invention, even in thecase of the breakage of the color wheel or the failure of the motor suchas with abnormal rotation speed or abnormal noises, the maintenance canbe easily performed by only detaching and replacing the color wheelunit.

According to the color wheel unit of the present invention, the lightincident/radiation opening of the color wheel case is sealed with thetransparent member, whereby when the color wheel is rotated at a highspeed, the reduction in display luminance, resulting from absorption(attraction) of dust or dirt in the air by charged color filters whichare made of glass can be prevented.

According to the color wheel unit of the present invention, the lightincident/radiating opening of the color wheel case is sealed with thetransparent member, and noises such as whistling sounds caused by thehigh-speed rotation of the color wheel or electromagnetic sounds of themotor can be excluded.

According to the color wheel unit of the present invention, thecushioning material is provided at the junction of the color wheel caselid and the color wheel case body, or the junction of the color wheelcase and the motor, whereby the noises such as whistling sounds causedby the high-speed rotation of the color wheel or electromagnetic soundsof the motor can be excluded.

Further, vibrations caused by rotational unbalance of the color wheel orthe motor can also be absorbed by the cushioning material which isprovided at the junction of the case and the motor, or at the fixingpart for fixing the color wheel unit body to the chassis or the like.

According to the field sequential color display device using the colorwheel unit of the present invention, the radiation fin which is providedon the color wheel case or the motor of the color wheel unit isair-cooled by the fan or the like, thereby effectively cooling the colorwheel case which is easily heated by the radiation heat from the lamp orabsorption of unnecessary light, whereby the reliability of the colorwheel and the motor therein can be increased.

According to the field sequential color display device using the colorwheel unit of the present invention, the color wheel unit is positionedinside an envelope in which the coolant is sealed, whereby the colorwheel case which is easily heated by the radiation heat from the lamp orabsorption of unnecessary light can be effectively cooled, and noisessuch as whistling sounds caused by the high-speed rotation of the colorwheel or electromagnetic sounds of the motor can be excluded.

According to the field sequential color display device of the presentinvention, the flare diaphragm is provided for shading part of lightwhich has been transmitted through the color wheel, and preventing lightof a color band different from a desired color which is to be displayedon the screen from being incident on the SLM, whereby the color mixturecan be prevented and bright and high-quality image displays can beobtained, without setting the black display period of the SLM to beunnecessarily long.

What is claimed is:
 1. A field sequential color display devicecomprising: a color wheel assembly comprising a color wheel divided intoa plurality of color regions and a motor containing a magnetic sensor ata fixed portion therein, said motor being adapted to rotate said colorwheel, wherein said magnetic sensor is operable to detect magnetism at arotation portion of said motor, and said magnetic sensor outputs atleast one pulse per revolution of said motor; and a spatial lightmodulator operable to display image data, said spatial light modulatorbeing driven in synchronization with the at least one pulse which isoutput by said magnetic sensor.
 2. A field sequential color displaydevice comprising: a color wheel assembly comprising a color wheeldivided into a plurality of color regions and a motor having a magneticsensor at a fixed portion therein, said motor being adapted to rotatesaid color wheel, wherein said motor and said color wheel are aligned toeach other, said magnetic sensor is operable to detect magnetism at arotation portion of said motor, and said magnetic sensor outputs atleast one pulse per revolution of said motor at designated colorswitching of said color wheel; and a spatial light modulator operable todisplay image data, said spatial light modulator being driven insynchronization with the at least one pulse which is output by saidmagnetic sensor.
 3. A field sequential color display device comprising:a color wheel assembly comprising a color wheel divided into a pluralityof color regions and a motor having a magnetic sensor at a fixed portiontherein, said motor being operable to rotate said color wheel, whereinsaid magnetic sensor is operable to detect magnetism at a rotationportion of said motor, and said magnetic sensor outputs at least onepulse per revolution of said motor; and a spatial light modulatoroperable to display image data, said spatial light modulator beingdriven in synchronization with a pulse obtained by electrically shiftinga phase of the at least one pulse output by said magnetic sensor forwardor backward.
 4. A field sequential color display device comprising: acolor wheel assembly comprising a color wheel divided into a pluralityof color regions and a motor having a magnetic sensor at a fixed portiontherein, said motor being adapted to rotate said color wheel, whereinsaid motor and said color wheel are aligned to each other, said magneticsensor is operable to detect magnetism at a rotation portion of saidmotor, and said magnetic sensor outputs at least one pulse perrevolution of said motor at designated color switching of said colorwheel; and a spatial light modulator operable to display image data,said spatial light modulator being driven in synchronization with apulse which is obtained by electrically shifting a phase of the at leastone pulse output by said magnetic sensor forward or backward.
 5. A fieldsequential color display device comprising: a light source; condensingmeans for condensing light emitted from said light source; a color wheelunit comprising a color wheel divided into red, green and blue regions,a motor adapted to rotate said color wheel, and a color wheel casehousing said color wheel and said motor, said color wheel unit beingoperable to selectively transmit or reflect light of red, green and bluebands in a predetermined order from the light which has been condensedby said condensing means; a spatial light modulator; illumination meansfor condensing the light transmitted or reflected by said color wheelunit, and illuminating said spatial light modulator, wherein saidspatial light modulator is operable to modulate the light incident fromsaid illumination means; and projection means for projecting the lightmodulated by said spatial light modulator on a screen, wherein saidcolor wheel unit is to be air-cooled by a fan, and a lightincident/radiating part of said color wheel case is sealed with alight-transmittable member.
 6. A field sequential color display devicecomprising: a light source; condensing means for condensing lightemitted from said light source; a color wheel unit comprising a colorwheel divided into red, green and blue regions, a motor adapted torotate said color wheel, and a color wheel case housing said color wheeland said motor, said color wheel unit being operable to selectivelytransmit or reflect light of red, green and blue bands in apredetermined order from the light which has been condensed by saidcondensing means; a spatial light modulator; illumination means forcondensing the light transmitted or reflected by said color wheel unit,and illuminating said spatial light modulator, wherein said spatiallight modulator is operable to modulate the light incident from saidillumination means; and projection means for projecting the lightmodulated by said spatial light modulator on a screen, wherein colorwheel unit is to be air-cooled by a fan, and a cushioning material isinserted at one of a junction of two portions of said color wheel case,a junction between said color wheel case and said motor, and a fixingpart for installing said color wheel case on a chassis.
 7. A fieldsequential color display device comprising: a light source; condensingmeans for condensing light emitted from said light source; a color wheelunit comprising a color wheel divided into red, green and blue regions,a motor adapted to rotate said color wheel, and a color wheel casehousing said color wheel and said motor, said color wheel unit beingoperable to selectively transmit or reflect light of red, green and bluebands in a predetermined order from the light condensed by saidcondensing means; a spatial light modulator; illumination means forcondensing the light transmitted or reflected by said color wheel unit,and illuminating said spatial light modulator, wherein said spatiallight modulator is operable to modulate the light incident from saidillumination means; projection means for projecting the light modulatedby said spatial light modulator on a screen; and an envelope filled witha liquid, said envelope being provided between said light source andsaid illumination means, and said color wheel unit being positioned insaid envelope, wherein a light incident/radiating part of said colorwheel case is sealed with a light-transmittable member.
 8. A fieldsequential color display device comprising: a light source; condensingmeans for condensing light emitted from said light source; a color wheelunit comprising a color wheel divided into red, green and blue regions,a motor adapted to rotate said color wheel, and a color wheel casehousing said color wheel and said motor, said color wheel unit beingoperable to selectively transmit or reflect light of red, green and bluebands in a predetermined order from the light condensed by saidcondensing means; a spatial light modulator; illumination means forcondensing the light transmitted or reflected by said color wheel unit,and illuminating said spatial light modulator, wherein said spatiallight modulator is operable to modulate the light incident from saidillumination means; projection means for projecting the light modulatedby said spatial light modulator on a screen; and an envelope filled witha liquid, said envelope being provided between said light source andsaid illumination means, and said color wheel unit being positioned insaid envelope, wherein a cushioning material is inserted at one of ajunction of two portions of said color wheel case, a junction betweensaid color wheel case and said motor, and a fixing part for installingsaid color wheel case on a chassis.
 9. A field sequential color displaydevice comprising: a light source; condensing means for condensing lightemitted from said light source; a color wheel for selectivelytransmitting or reflecting light of red, green and blue bands in apredetermined order from the light condensed by said condensing means; aspatial modulator; illumination means for condensing the lighttransmitted or reflected by said color wheel, and illuminating saidspatial light modulator, wherein said spatial light modulator isoperable to modulate the light incident from said illumination means;projection means for projecting the light modulated by said spatiallight modulator on a screen; and shading means for shading a part of thelight incident on said color wheel or the light transmitted or reflectedby said color wheel, by controlling an opening in a rotational directionof said color wheel.
 10. The field sequential color display device ofclaim 9, wherein a size of said light transmission part of said shadingmeans varies with a wavelength of the light transmitted or reflected bysaid color wheel.
 11. The field sequential color display device of claim9, further comprising: light elimination means for eliminating part oflight of a specific wavelength band from the light incident on saidlight transmission part of said shading means.
 12. The field sequentialcolor display device of claim 9, wherein said shading means ispositioned on a radiation side of said color wheel.
 13. The fieldsequential color display device of claim 9, wherein said shading meansis positioned at a 5 mm or less air gap with said color wheel.
 14. Thefield sequential color display device of claim 9, wherein said lightsource is an extra-high pressure mercury lamp.
 15. The field sequentialcolor display device of claim 9, wherein a plane of said shading meansorthogonal to an optical axis of said shading means is approximatelycircular in cross section.
 16. The field sequential color display deviceof claim 9, wherein said condensing means is an ellipsoidal mirror. 17.The field sequential color display device of claim 16, wherein saidcolor wheel has a light transmitting surface or a light reflectingsurface which is positioned in a vicinity of a long focus of saidellipsoidal mirror.
 18. The field sequential color display device ofclaim 9, wherein said color wheel comprises fan-shaped red, green andblue color filters which are positioned in a form of a disk, and saidcolor wheel successively transmits the light of the respective red,green and blue bands by rotation.
 19. The field sequential color displaydevice of claim 18, wherein said shading means shades part of incidentlight with respect to a rotational direction of said color wheel, butdoes not shade the light with respect to a radial direction of saidcolor wheel.
 20. The field sequential color display device of claim 19,wherein said shading means is a diaphragm having an opening of apredetermined size through which the incident light is passed, anopening width of said diaphragm with respect to the rotational directionof said color wheel is set to be equivalent to or smaller than adiameter of a condensation spot which is formed on said color wheel inan initial stage of use of said light source, and an opening width ofsaid diaphragm with respect to the radial direction of said color wheelis set to be larger than the diameter of the condensation spot.